Mouse Lock is currently supported in Pepper, but not yet supported from WebKit.

Move the render thread logic for managing the mouse lock state out of the pepper_plugin_delegate_impl, and into a higher level dispatcher for render_view_impl.

Handle mouse lock / pointer lock requests from both pepper and webkit (WebKit API not yet landed, small TODOs left in this code to enable once that lands).

BUG=109957
TEST=Pepper examples/mouse_lock and NaCl mouse lock examples still work.

Review URL: http://codereview.chromium.org/8970016

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@119206 0039d316-1c4b-4281-b951-d872f2087c98

16 files changed, 662 insertions, 204 deletions

diff --git a/content/content_renderer.gypi b/content/content_renderer.gypi
index 36c0ac9..d19db89 100644
--- a/content/content_renderer.gypi
+++ b/content/content_renderer.gypi
@@ -125,6 +125,8 @@
     'renderer/media/video_capture_message_filter.h',
     'renderer/mhtml_generator.cc',
     'renderer/mhtml_generator.h',
+    'renderer/mouse_lock_dispatcher.cc',
+    'renderer/mouse_lock_dispatcher.h',
     'renderer/notification_provider.cc',
     'renderer/notification_provider.h',
     'renderer/paint_aggregator.cc',
diff --git a/content/content_tests.gypi b/content/content_tests.gypi
index 9c380d4..1803ce4 100644
--- a/content/content_tests.gypi
+++ b/content/content_tests.gypi
@@ -285,6 +285,7 @@
         'renderer/media/video_capture_impl_unittest.cc',
         'renderer/media/video_capture_message_filter_unittest.cc',
         'renderer/media/webrtc_audio_device_unittest.cc',
+        'renderer/mouse_lock_dispatcher_unittest.cc',
         'renderer/paint_aggregator_unittest.cc',
         'renderer/pepper_plugin_delegate_impl_unittest.cc',
         'renderer/v8_value_converter_impl_unittest.cc',
diff --git a/content/renderer/mouse_lock_dispatcher.cc b/content/renderer/mouse_lock_dispatcher.cc
new file mode 100644
index 0000000..41ed654
--- /dev/null
+++ b/content/renderer/mouse_lock_dispatcher.cc
@@ -0,0 +1,117 @@
+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "content/renderer/mouse_lock_dispatcher.h"
+
+#include "content/common/view_messages.h"
+#include "content/renderer/render_view_impl.h"
+#include "third_party/WebKit/Source/WebKit/chromium/public/WebInputEvent.h"
+#include "third_party/WebKit/Source/WebKit/chromium/public/WebWidget.h"
+
+MouseLockDispatcher::MouseLockDispatcher(RenderViewImpl* render_view_impl)
+    : content::RenderViewObserver(render_view_impl),
+      render_view_impl_(render_view_impl),
+      mouse_locked_(false),
+      pending_lock_request_(false),
+      pending_unlock_request_(false),
+      target_(NULL) {
+}
+
+MouseLockDispatcher::~MouseLockDispatcher() {
+}
+
+bool MouseLockDispatcher::LockMouse(LockTarget* target) {
+  if (MouseLockedOrPendingAction())
+    return false;
+
+  pending_lock_request_ = true;
+  target_ = target;
+
+  Send(new ViewHostMsg_LockMouse(routing_id()));
+  return true;
+}
+
+void MouseLockDispatcher::UnlockMouse(LockTarget* target) {
+  if (target && target == target_ && !pending_unlock_request_) {
+    pending_unlock_request_ = true;
+    Send(new ViewHostMsg_UnlockMouse(routing_id()));
+  }
+}
+
+void MouseLockDispatcher::OnLockTargetDestroyed(LockTarget* target) {
+  if (target == target_) {
+    UnlockMouse(target);
+    target_ = NULL;
+  }
+}
+
+bool MouseLockDispatcher::IsMouseLockedTo(LockTarget* target) {
+  return mouse_locked_ && target_ == target;
+}
+
+bool MouseLockDispatcher::WillHandleMouseEvent(
+    const WebKit::WebMouseEvent& event) {
+  if (mouse_locked_ && target_)
+    return target_->HandleMouseLockedInputEvent(event);
+  return false;
+}
+
+bool MouseLockDispatcher::OnMessageReceived(const IPC::Message& message) {
+  bool handled = true;
+  IPC_BEGIN_MESSAGE_MAP(MouseLockDispatcher, message)
+    IPC_MESSAGE_HANDLER(ViewMsg_LockMouse_ACK, OnLockMouseACK)
+    IPC_MESSAGE_HANDLER(ViewMsg_MouseLockLost, OnMouseLockLost)
+    IPC_MESSAGE_UNHANDLED(handled = false)
+  IPC_END_MESSAGE_MAP()
+  return handled;
+}
+
+void MouseLockDispatcher::OnLockMouseACK(bool succeeded) {
+  DCHECK(!mouse_locked_ && pending_lock_request_);
+
+  mouse_locked_ = succeeded;
+  pending_lock_request_ = false;
+  if (pending_unlock_request_ && !succeeded) {
+    // We have sent an unlock request after the lock request. However, since
+    // the lock request has failed, the unlock request will be ignored by the
+    // browser side and there won't be any response to it.
+    pending_unlock_request_ = false;
+  }
+
+  LockTarget* last_target = target_;
+  if (!succeeded)
+    target_ = NULL;
+
+  // Callbacks made after all state modification to prevent reentrant errors
+  // such as OnLockMouseACK() synchronously calling LockMouse().
+
+  if (last_target)
+    last_target->OnLockMouseACK(succeeded);
+
+  // Mouse Lock removes the system cursor and provides all mouse motion as
+  // .movementX/Y values on events all sent to a fixed target. This requires
+  // content to specifically request the mode to be entered.
+  // Mouse Capture is implicitly given for the duration of a drag event, and
+  // sends all mouse events to the initial target of the drag.
+  // If Lock is entered it supercedes any in progress Capture.
+  if (succeeded && render_view_impl_->webwidget())
+      render_view_impl_->webwidget()->mouseCaptureLost();
+}
+
+void MouseLockDispatcher::OnMouseLockLost() {
+  DCHECK(mouse_locked_ && !pending_lock_request_);
+
+  mouse_locked_ = false;
+  pending_unlock_request_ = false;
+
+  LockTarget* last_target = target_;
+  target_ = NULL;
+
+  // Callbacks made after all state modification to prevent reentrant errors
+  // such as OnMouseLockLost() synchronously calling LockMouse().
+
+  if (last_target)
+    last_target->OnMouseLockLost();
+}
+
diff --git a/content/renderer/mouse_lock_dispatcher.h b/content/renderer/mouse_lock_dispatcher.h
new file mode 100644
index 0000000..1520e38
--- /dev/null
+++ b/content/renderer/mouse_lock_dispatcher.h
@@ -0,0 +1,87 @@
+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CONTENT_RENDERER_MOUSE_LOCK_DISPATCHER_H_
+#define CONTENT_RENDERER_MOUSE_LOCK_DISPATCHER_H_
+#pragma once
+
+#include "base/basictypes.h"
+#include "content/public/renderer/render_view_observer.h"
+
+class RenderViewImpl;
+
+namespace WebKit {
+class WebMouseEvent;
+class WebWidget;
+}  // namespace WebKit
+
+namespace webkit{
+namespace ppapi {
+class PluginInstance;
+}  // namespace ppapi
+}  // namespace webkit
+
+// MouseLockDispatcher is owned by RenderViewImpl.
+class MouseLockDispatcher : public content::RenderViewObserver {
+ public:
+  explicit MouseLockDispatcher(RenderViewImpl* render_view_impl);
+  virtual ~MouseLockDispatcher();
+
+  class LockTarget {
+   public:
+    virtual ~LockTarget() {}
+    // A mouse lock request was pending and this reports success or failure.
+    virtual void OnLockMouseACK(bool succeeded) = 0;
+    // A mouse lock was in place, but has been lost.
+    virtual void OnMouseLockLost() = 0;
+    // A mouse lock is enabled and mouse events are being delievered.
+    virtual bool HandleMouseLockedInputEvent(
+        const WebKit::WebMouseEvent& event) = 0;
+  };
+
+  // Locks the mouse to the |target|. If true is returned, an asynchronous
+  // response to target->OnLockMouseACK() will follow.
+  bool LockMouse(LockTarget* target);
+  // Request to unlock the mouse. An asynchronous response to
+  // target->OnMouseLockLost() will follow.
+  void UnlockMouse(LockTarget* target);
+  // Clears out the reference to the |target| because it has or is being
+  // destroyed. Unlocks if locked. The pointer will not be accessed.
+  void OnLockTargetDestroyed(LockTarget* target);
+  bool IsMouseLockedTo(LockTarget* target);
+
+  // Allow lock target to consumed a mouse event, if it does return true.
+  bool WillHandleMouseEvent(const WebKit::WebMouseEvent& event);
+
+ private:
+  // RenderView::Observer implementation.
+  virtual bool OnMessageReceived(const IPC::Message& message) OVERRIDE;
+
+  // IPC handlers.
+  void OnLockMouseACK(bool succeeded);
+  void OnMouseLockLost();
+
+  bool MouseLockedOrPendingAction() const {
+    return mouse_locked_ || pending_lock_request_ || pending_unlock_request_;
+  }
+
+  RenderViewImpl* render_view_impl_;
+
+  bool mouse_locked_;
+  // If both |pending_lock_request_| and |pending_unlock_request_| are true,
+  // it means a lock request was sent before an unlock request and we haven't
+  // received responses for them. The logic in LockMouse() makes sure that a
+  // lock request won't be sent when there is a pending unlock request.
+  bool pending_lock_request_;
+  bool pending_unlock_request_;
+
+  // |target_| is the pending or current owner of mouse lock. We retain a non
+  // owning reference here that must be cleared by |OnLockTargetDestroyed|
+  // when it is destroyed.
+  LockTarget* target_;
+
+  DISALLOW_COPY_AND_ASSIGN(MouseLockDispatcher);
+};
+
+#endif  // CONTENT_RENDERER_MOUSE_LOCK_DISPATCHER_H_
diff --git a/content/renderer/mouse_lock_dispatcher_unittest.cc b/content/renderer/mouse_lock_dispatcher_unittest.cc
new file mode 100644
index 0000000..5605aa4
--- /dev/null
+++ b/content/renderer/mouse_lock_dispatcher_unittest.cc
@@ -0,0 +1,232 @@
+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include <string>
+
+#include "content/common/view_messages.h"
+#include "content/renderer/mouse_lock_dispatcher.h"
+#include "content/renderer/render_view_impl.h"
+#include "content/test/render_view_test.h"
+#include "testing/gmock/include/gmock/gmock.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+using ::testing::_;
+
+namespace {
+
+class MockLockTarget : public MouseLockDispatcher::LockTarget {
+ public:
+   MOCK_METHOD1(OnLockMouseACK, void(bool));
+   MOCK_METHOD0(OnMouseLockLost, void());
+   MOCK_METHOD1(HandleMouseLockedInputEvent,
+                bool(const WebKit::WebMouseEvent&));
+};
+
+// MouseLockDispatcher is a RenderViewObserver, and we test it by creating a
+// fixture containing a RenderViewImpl view() and interacting to that interface.
+class MouseLockDispatcherTest
+    : public content::RenderViewTest {
+ public:
+  virtual void SetUp() {
+    content::RenderViewTest::SetUp();
+    route_id_ = view()->GetRoutingId();
+    target_ = new MockLockTarget();
+    alternate_target_ = new MockLockTarget();
+  }
+
+  virtual void TearDown() {
+    content::RenderViewTest::TearDown();
+    delete target_;
+    delete alternate_target_;
+  }
+
+ protected:
+  RenderViewImpl* view() { return static_cast<RenderViewImpl*>(view_); }
+  MouseLockDispatcher* dispatcher() { return view()->mouse_lock_dispatcher(); }
+  int route_id_;
+  MockLockTarget* target_;
+  MockLockTarget* alternate_target_;
+};
+
+}  // namespace
+
+// Test simple use of RenderViewImpl interface to WebKit for pointer lock.
+TEST_F(MouseLockDispatcherTest, BasicWebWidget) {
+  // Start unlocked.
+  EXPECT_FALSE(view()->isPointerLocked());
+
+  // Lock.
+  EXPECT_TRUE(view()->requestPointerLock());
+  view()->OnMessageReceived(ViewMsg_LockMouse_ACK(route_id_, true));
+  EXPECT_TRUE(view()->isPointerLocked());
+
+  // Unlock.
+  view()->requestPointerUnlock();
+  view()->OnMessageReceived(ViewMsg_MouseLockLost(route_id_));
+  EXPECT_FALSE(view()->isPointerLocked());
+
+  // Attempt a lock, and have it fail.
+  EXPECT_TRUE(view()->requestPointerLock());
+  view()->OnMessageReceived(ViewMsg_LockMouse_ACK(route_id_, false));
+  EXPECT_FALSE(view()->isPointerLocked());
+}
+
+// Test simple use of MouseLockDispatcher with a mock LockTarget.
+TEST_F(MouseLockDispatcherTest, BasicMockLockTarget) {
+  ::testing::InSequence expect_calls_in_sequence;
+  EXPECT_CALL(*target_, OnLockMouseACK(true));
+  EXPECT_CALL(*target_, HandleMouseLockedInputEvent(_));
+  EXPECT_CALL(*target_, OnMouseLockLost());
+  EXPECT_CALL(*target_, OnLockMouseACK(false));
+
+  // Start unlocked.
+  EXPECT_FALSE(dispatcher()->IsMouseLockedTo(NULL));
+  EXPECT_FALSE(dispatcher()->IsMouseLockedTo(target_));
+
+  // Lock.
+  EXPECT_TRUE(dispatcher()->LockMouse(target_));
+  view()->OnMessageReceived(ViewMsg_LockMouse_ACK(route_id_, true));
+  EXPECT_TRUE(dispatcher()->IsMouseLockedTo(target_));
+
+  // Receive mouse event.
+  dispatcher()->WillHandleMouseEvent(WebKit::WebMouseEvent());
+
+  // Unlock.
+  dispatcher()->UnlockMouse(target_);
+  view()->OnMessageReceived(ViewMsg_MouseLockLost(route_id_));
+  EXPECT_FALSE(dispatcher()->IsMouseLockedTo(target_));
+
+  // Attempt a lock, and have it fail.
+  EXPECT_TRUE(dispatcher()->LockMouse(target_));
+  view()->OnMessageReceived(ViewMsg_LockMouse_ACK(route_id_, false));
+  EXPECT_FALSE(dispatcher()->IsMouseLockedTo(target_));
+}
+
+// Test deleting a target while it is in use by MouseLockDispatcher.
+TEST_F(MouseLockDispatcherTest, DeleteAndUnlock) {
+  ::testing::InSequence expect_calls_in_sequence;
+  EXPECT_CALL(*target_, OnLockMouseACK(true));
+  EXPECT_CALL(*target_, HandleMouseLockedInputEvent(_)).Times(0);
+  EXPECT_CALL(*target_, OnMouseLockLost()).Times(0);
+
+  // Lock.
+  EXPECT_TRUE(dispatcher()->LockMouse(target_));
+  view()->OnMessageReceived(ViewMsg_LockMouse_ACK(route_id_, true));
+  EXPECT_TRUE(dispatcher()->IsMouseLockedTo(target_));
+
+  // Unlock, with a deleted target.
+  // Don't receive mouse events or lock lost.
+  dispatcher()->OnLockTargetDestroyed(target_);
+  delete target_;
+  target_ = NULL;
+  dispatcher()->WillHandleMouseEvent(WebKit::WebMouseEvent());
+  view()->OnMessageReceived(ViewMsg_MouseLockLost(route_id_));
+  EXPECT_FALSE(dispatcher()->IsMouseLockedTo(target_));
+}
+
+// Test deleting a target that is pending a lock request response.
+TEST_F(MouseLockDispatcherTest, DeleteWithPendingLockSuccess) {
+  ::testing::InSequence expect_calls_in_sequence;
+  EXPECT_CALL(*target_, OnLockMouseACK(true)).Times(0);
+  EXPECT_CALL(*target_, OnMouseLockLost()).Times(0);
+
+  // Lock request.
+  EXPECT_TRUE(dispatcher()->LockMouse(target_));
+
+  // Before receiving response delete the target.
+  dispatcher()->OnLockTargetDestroyed(target_);
+  delete target_;
+  target_ = NULL;
+
+  // Lock response.
+  view()->OnMessageReceived(ViewMsg_LockMouse_ACK(route_id_, true));
+}
+
+// Test deleting a target that is pending a lock request failure response.
+TEST_F(MouseLockDispatcherTest, DeleteWithPendingLockFail) {
+  ::testing::InSequence expect_calls_in_sequence;
+  EXPECT_CALL(*target_, OnLockMouseACK(true)).Times(0);
+  EXPECT_CALL(*target_, OnMouseLockLost()).Times(0);
+
+  // Lock request.
+  EXPECT_TRUE(dispatcher()->LockMouse(target_));
+
+  // Before receiving response delete the target.
+  dispatcher()->OnLockTargetDestroyed(target_);
+  delete target_;
+  target_ = NULL;
+
+  // Lock response.
+  view()->OnMessageReceived(ViewMsg_LockMouse_ACK(route_id_, false));
+}
+
+// Test not receiving mouse events when a target is not locked.
+TEST_F(MouseLockDispatcherTest, MouseEventsNotReceived) {
+  ::testing::InSequence expect_calls_in_sequence;
+  EXPECT_CALL(*target_, HandleMouseLockedInputEvent(_)).Times(0);
+  EXPECT_CALL(*target_, OnLockMouseACK(true));
+  EXPECT_CALL(*target_, HandleMouseLockedInputEvent(_));
+  EXPECT_CALL(*target_, OnMouseLockLost());
+  EXPECT_CALL(*target_, HandleMouseLockedInputEvent(_)).Times(0);
+
+  // (Don't) receive mouse event.
+  dispatcher()->WillHandleMouseEvent(WebKit::WebMouseEvent());
+
+  // Lock.
+  EXPECT_TRUE(dispatcher()->LockMouse(target_));
+  view()->OnMessageReceived(ViewMsg_LockMouse_ACK(route_id_, true));
+  EXPECT_TRUE(dispatcher()->IsMouseLockedTo(target_));
+
+  // Receive mouse event.
+  dispatcher()->WillHandleMouseEvent(WebKit::WebMouseEvent());
+
+  // Unlock.
+  dispatcher()->UnlockMouse(target_);
+  view()->OnMessageReceived(ViewMsg_MouseLockLost(route_id_));
+  EXPECT_FALSE(dispatcher()->IsMouseLockedTo(target_));
+
+  // (Don't) receive mouse event.
+  dispatcher()->WillHandleMouseEvent(WebKit::WebMouseEvent());
+}
+
+// Test multiple targets
+TEST_F(MouseLockDispatcherTest, MultipleTargets) {
+  ::testing::InSequence expect_calls_in_sequence;
+  EXPECT_CALL(*target_, OnLockMouseACK(true));
+  EXPECT_CALL(*target_, HandleMouseLockedInputEvent(_));
+  EXPECT_CALL(*alternate_target_, HandleMouseLockedInputEvent(_)).Times(0);
+  EXPECT_CALL(*target_, OnMouseLockLost()).Times(0);
+  EXPECT_CALL(*alternate_target_, OnMouseLockLost()).Times(0);
+  EXPECT_CALL(*target_, OnMouseLockLost());
+
+  // Lock request for target.
+  EXPECT_TRUE(dispatcher()->LockMouse(target_));
+
+  // Fail attempt to lock alternate.
+  EXPECT_FALSE(dispatcher()->IsMouseLockedTo(alternate_target_));
+  EXPECT_FALSE(dispatcher()->LockMouse(alternate_target_));
+
+  // Lock completion for target.
+  view()->OnMessageReceived(ViewMsg_LockMouse_ACK(route_id_, true));
+  EXPECT_TRUE(dispatcher()->IsMouseLockedTo(target_));
+
+  // Fail attempt to lock alternate.
+  EXPECT_FALSE(dispatcher()->IsMouseLockedTo(alternate_target_));
+  EXPECT_FALSE(dispatcher()->LockMouse(alternate_target_));
+
+  // Receive mouse event to only one target.
+  dispatcher()->WillHandleMouseEvent(WebKit::WebMouseEvent());
+
+  // Unlock alternate target has no effect.
+  dispatcher()->UnlockMouse(alternate_target_);
+  EXPECT_TRUE(dispatcher()->IsMouseLockedTo(target_));
+  EXPECT_FALSE(dispatcher()->IsMouseLockedTo(alternate_target_));
+
+  // Though the call to UnlockMouse should not unlock any target, we will
+  // cause an unlock (as if e.g. user escaped mouse lock) and verify the
+  // correct target is unlocked.
+  view()->OnMessageReceived(ViewMsg_MouseLockLost(route_id_));
+  EXPECT_FALSE(dispatcher()->IsMouseLockedTo(target_));
+}
+
diff --git a/content/renderer/pepper_plugin_delegate_impl.cc b/content/renderer/pepper_plugin_delegate_impl.cc
index ffc7fc1..3c4bc63 100644
--- a/content/renderer/pepper_plugin_delegate_impl.cc
+++ b/content/renderer/pepper_plugin_delegate_impl.cc
@@ -644,6 +644,29 @@ class PlatformVideoCaptureImpl
   media::VideoCapture* video_capture_;
 };
 
+class PluginInstanceLockTarget : public MouseLockDispatcher::LockTarget {
+ public:
+  PluginInstanceLockTarget(webkit::ppapi::PluginInstance* plugin)
+      : plugin_(plugin) {}
+
+  virtual void OnLockMouseACK(bool succeeded) OVERRIDE {
+    plugin_->OnLockMouseACK(succeeded);
+  }
+
+  virtual void OnMouseLockLost() OVERRIDE {
+    plugin_->OnMouseLockLost();
+  }
+
+  virtual bool HandleMouseLockedInputEvent(
+      const WebKit::WebMouseEvent &event) OVERRIDE {
+    plugin_->HandleMouseLockedInputEvent(event);
+    return true;
+  }
+
+ private:
+  webkit::ppapi::PluginInstance* plugin_;
+};
+
 }  // namespace
 
 BrokerDispatcherWrapper::BrokerDispatcherWrapper() {
@@ -850,15 +873,11 @@ PepperPluginDelegateImpl::PepperPluginDelegateImpl(RenderViewImpl* render_view)
       has_saved_context_menu_action_(false),
       saved_context_menu_action_(0),
       focused_plugin_(NULL),
-      mouse_lock_owner_(NULL),
-      mouse_locked_(false),
-      pending_lock_request_(false),
-      pending_unlock_request_(false),
       last_mouse_event_target_(NULL) {
 }
 
 PepperPluginDelegateImpl::~PepperPluginDelegateImpl() {
-  DCHECK(!mouse_lock_owner_);
+  DCHECK(mouse_lock_instances_.empty());
 }
 
 scoped_refptr<webkit::ppapi::PluginModule>
@@ -1146,8 +1165,7 @@ bool PepperPluginDelegateImpl::CanComposeInline() const {
 void PepperPluginDelegateImpl::PluginCrashed(
     webkit::ppapi::PluginInstance* instance) {
   render_view_->PluginCrashed(instance->module()->path());
-
-  UnlockMouse(instance);
+  UnSetAndDeleteLockTargetAdapter(instance);
 }
 
 void PepperPluginDelegateImpl::InstanceCreated(
@@ -1161,14 +1179,8 @@ void PepperPluginDelegateImpl::InstanceCreated(
 void PepperPluginDelegateImpl::InstanceDeleted(
     webkit::ppapi::PluginInstance* instance) {
   active_instances_.erase(instance);
+  UnSetAndDeleteLockTargetAdapter(instance);
 
-  if (mouse_lock_owner_ && mouse_lock_owner_ == instance) {
-    // UnlockMouse() will determine whether a ViewHostMsg_UnlockMouse needs to
-    // be sent, and set internal state properly. We only need to forget about
-    // the current |mouse_lock_owner_|.
-    UnlockMouse(mouse_lock_owner_);
-    mouse_lock_owner_ = NULL;
-  }
   if (last_mouse_event_target_ == instance)
     last_mouse_event_target_ = NULL;
   if (focused_plugin_ == instance)
@@ -1359,50 +1371,7 @@ bool PepperPluginDelegateImpl::IsPluginFocused() const {
   return focused_plugin_ != NULL;
 }
 
-void PepperPluginDelegateImpl::OnLockMouseACK(bool succeeded) {
-  DCHECK(!mouse_locked_ && pending_lock_request_);
-
-  mouse_locked_ = succeeded;
-  pending_lock_request_ = false;
-  if (pending_unlock_request_ && !succeeded) {
-    // We have sent an unlock request after the lock request. However, since
-    // the lock request has failed, the unlock request will be ignored by the
-    // browser side and there won't be any response to it.
-    pending_unlock_request_ = false;
-  }
-  // If the PluginInstance has been deleted, |mouse_lock_owner_| can be NULL.
-  if (mouse_lock_owner_) {
-    webkit::ppapi::PluginInstance* last_mouse_lock_owner = mouse_lock_owner_;
-    if (!succeeded) {
-      // Reset |mouse_lock_owner_| to NULL before calling OnLockMouseACK(), so
-      // that if OnLockMouseACK() results in calls to any mouse lock method
-      // (e.g., LockMouse()), the method will see consistent internal state.
-      mouse_lock_owner_ = NULL;
-    }
-
-    last_mouse_lock_owner->OnLockMouseACK(succeeded ? PP_OK : PP_ERROR_FAILED);
-  }
-}
-
-void PepperPluginDelegateImpl::OnMouseLockLost() {
-  DCHECK(mouse_locked_ && !pending_lock_request_);
-
-  mouse_locked_ = false;
-  pending_unlock_request_ = false;
-  // If the PluginInstance has been deleted, |mouse_lock_owner_| can be NULL.
-  if (mouse_lock_owner_) {
-    // Reset |mouse_lock_owner_| to NULL before calling OnMouseLockLost(), so
-    // that if OnMouseLockLost() results in calls to any mouse lock method
-    // (e.g., LockMouse()), the method will see consistent internal state.
-    webkit::ppapi::PluginInstance* last_mouse_lock_owner = mouse_lock_owner_;
-    mouse_lock_owner_ = NULL;
-
-    last_mouse_lock_owner->OnMouseLockLost();
-  }
-}
-
-bool PepperPluginDelegateImpl::HandleMouseEvent(
-    const WebKit::WebMouseEvent& event) {
+void PepperPluginDelegateImpl::WillHandleMouseEvent() {
   // This method is called for every mouse event that the render view receives.
   // And then the mouse event is forwarded to WebKit, which dispatches it to the
   // event target. Potentially a Pepper plugin will receive the event.
@@ -1411,19 +1380,6 @@ bool PepperPluginDelegateImpl::HandleMouseEvent(
   // event, it will notify us via DidReceiveMouseEvent() and set itself as
   // |last_mouse_event_target_|.
   last_mouse_event_target_ = NULL;
-
-  if (mouse_locked_) {
-    if (mouse_lock_owner_) {
-      // |cursor_info| is ignored since it is hidden when the mouse is locked.
-      WebKit::WebCursorInfo cursor_info;
-      mouse_lock_owner_->HandleInputEvent(event, &cursor_info);
-    }
-
-    // If the mouse is locked, only the current owner of the mouse lock can
-    // process mouse events.
-    return true;
-  }
-  return false;
 }
 
 bool PepperPluginDelegateImpl::OpenFileSystem(
@@ -1961,56 +1917,23 @@ ppapi::Preferences PepperPluginDelegateImpl::GetPreferences() {
   return ppapi::Preferences(render_view_->webkit_preferences());
 }
 
-void PepperPluginDelegateImpl::LockMouse(
+bool PepperPluginDelegateImpl::LockMouse(
     webkit::ppapi::PluginInstance* instance) {
-  DCHECK(instance);
-  if (!MouseLockedOrPending()) {
-    DCHECK(!mouse_lock_owner_);
-    pending_lock_request_ = true;
-    mouse_lock_owner_ = instance;
-
-    render_view_->Send(
-        new ViewHostMsg_LockMouse(render_view_->routing_id()));
-  } else if (instance != mouse_lock_owner_) {
-    // Another plugin instance is using mouse lock. Fail immediately.
-    instance->OnLockMouseACK(PP_ERROR_FAILED);
-  } else {
-    if (mouse_locked_) {
-      instance->OnLockMouseACK(PP_OK);
-    } else if (pending_lock_request_) {
-      instance->OnLockMouseACK(PP_ERROR_INPROGRESS);
-    } else {
-      // The only case left here is
-      // !mouse_locked_ && !pending_lock_request_ && pending_unlock_request_,
-      // which is not possible.
-      NOTREACHED();
-      instance->OnLockMouseACK(PP_ERROR_FAILED);
-    }
-  }
+
+  return render_view_->mouse_lock_dispatcher()->LockMouse(
+      GetOrCreateLockTargetAdapter(instance));
 }
 
 void PepperPluginDelegateImpl::UnlockMouse(
     webkit::ppapi::PluginInstance* instance) {
-  DCHECK(instance);
-
-  // If no one is using mouse lock or the user is not |instance|, ignore
-  // the unlock request.
-  if (MouseLockedOrPending() && mouse_lock_owner_ == instance) {
-    if (mouse_locked_ || pending_lock_request_) {
-      DCHECK(!mouse_locked_ || !pending_lock_request_);
-      if (!pending_unlock_request_) {
-        pending_unlock_request_ = true;
-
-        render_view_->Send(
-            new ViewHostMsg_UnlockMouse(render_view_->routing_id()));
-      }
-    } else {
-      // The only case left here is
-      // !mouse_locked_ && !pending_lock_request_ && pending_unlock_request_,
-      // which is not possible.
-      NOTREACHED();
-    }
-  }
+  render_view_->mouse_lock_dispatcher()->UnlockMouse(
+      GetOrCreateLockTargetAdapter(instance));
+}
+
+bool PepperPluginDelegateImpl::IsMouseLocked(
+    webkit::ppapi::PluginInstance* instance) {
+  return render_view_->mouse_lock_dispatcher()->IsMouseLockedTo(
+      GetOrCreateLockTargetAdapter(instance));
 }
 
 void PepperPluginDelegateImpl::DidChangeCursor(
@@ -2170,3 +2093,25 @@ bool PepperPluginDelegateImpl::CanUseSocketAPIs() {
 
   return content::GetContentClient()->renderer()->AllowSocketAPI(url);
 }
+
+MouseLockDispatcher::LockTarget*
+    PepperPluginDelegateImpl::GetOrCreateLockTargetAdapter(
+    webkit::ppapi::PluginInstance* instance) {
+  MouseLockDispatcher::LockTarget* target = mouse_lock_instances_[instance];
+  if (target)
+    return target;
+
+  return mouse_lock_instances_[instance] =
+      new PluginInstanceLockTarget(instance);
+}
+
+void PepperPluginDelegateImpl::UnSetAndDeleteLockTargetAdapter(
+    webkit::ppapi::PluginInstance* instance) {
+  LockTargetMap::iterator it = mouse_lock_instances_.find(instance);
+  if (it != mouse_lock_instances_.end()) {
+    MouseLockDispatcher::LockTarget* target = it->second;
+    render_view_->mouse_lock_dispatcher()->OnLockTargetDestroyed(target);
+    delete target;
+    mouse_lock_instances_.erase(it);
+  }
+}
diff --git a/content/renderer/pepper_plugin_delegate_impl.h b/content/renderer/pepper_plugin_delegate_impl.h
index 22f5ab2..22de0d5 100644
--- a/content/renderer/pepper_plugin_delegate_impl.h
+++ b/content/renderer/pepper_plugin_delegate_impl.h
@@ -16,6 +16,7 @@
 #include "base/memory/weak_ptr.h"
 #include "content/common/content_export.h"
 #include "content/public/renderer/render_view_observer.h"
+#include "content/renderer/mouse_lock_dispatcher.h"
 #include "content/renderer/pepper_parent_context_provider.h"
 #include "ppapi/proxy/broker_dispatcher.h"
 #include "ppapi/proxy/proxy_channel.h"
@@ -197,15 +198,8 @@ class PepperPluginDelegateImpl
       int selection_end);
   void OnImeConfirmComposition(const string16& text);
 
-  // Notification that the request to lock the mouse has completed.
-  void OnLockMouseACK(bool succeeded);
-  // Notification that the plugin instance has lost the mouse lock.
-  void OnMouseLockLost();
   // Notification that a mouse event has arrived at the render view.
-  // Returns true if no further handling is needed. For example, if the mouse is
-  // currently locked, this method directly dispatches the event to the owner of
-  // the mouse lock and returns true.
-  bool HandleMouseEvent(const WebKit::WebMouseEvent& event);
+  void WillHandleMouseEvent();
 
   // PluginDelegate implementation.
   virtual void PluginFocusChanged(webkit::ppapi::PluginInstance* instance,
@@ -383,8 +377,9 @@ class PepperPluginDelegateImpl
   virtual base::SharedMemory* CreateAnonymousSharedMemory(uint32_t size)
       OVERRIDE;
   virtual ::ppapi::Preferences GetPreferences() OVERRIDE;
-  virtual void LockMouse(webkit::ppapi::PluginInstance* instance) OVERRIDE;
+  virtual bool LockMouse(webkit::ppapi::PluginInstance* instance) OVERRIDE;
   virtual void UnlockMouse(webkit::ppapi::PluginInstance* instance) OVERRIDE;
+  virtual bool IsMouseLocked(webkit::ppapi::PluginInstance* instance) OVERRIDE;
   virtual void DidChangeCursor(webkit::ppapi::PluginInstance* instance,
                                const WebKit::WebCursorInfo& cursor) OVERRIDE;
   virtual void DidReceiveMouseEvent(
@@ -433,10 +428,6 @@ class PepperPluginDelegateImpl
   scoped_refptr<PpapiBrokerImpl> CreatePpapiBroker(
       webkit::ppapi::PluginModule* plugin_module);
 
-  bool MouseLockedOrPending() const {
-    return mouse_locked_ || pending_lock_request_ || pending_unlock_request_;
-  }
-
   // Implementation of PepperParentContextProvider.
   virtual RendererGLContext* GetParentContextForPlatformContext3D() OVERRIDE;
 
@@ -450,10 +441,17 @@ class PepperPluginDelegateImpl
   // cases and do the check during socket creation in the browser process.
   bool CanUseSocketAPIs();
 
+  MouseLockDispatcher::LockTarget* GetOrCreateLockTargetAdapter(
+      webkit::ppapi::PluginInstance* instance);
+  void UnSetAndDeleteLockTargetAdapter(webkit::ppapi::PluginInstance* instance);
+
   // Pointer to the RenderView that owns us.
   RenderViewImpl* render_view_;
 
   std::set<webkit::ppapi::PluginInstance*> active_instances_;
+  typedef std::map<webkit::ppapi::PluginInstance*,
+                   MouseLockDispatcher::LockTarget*> LockTargetMap;
+  LockTargetMap mouse_lock_instances_;
 
   // Used to send a single context menu "completion" upon menu close.
   bool has_saved_context_menu_action_;
@@ -481,21 +479,6 @@ class PepperPluginDelegateImpl
   // progress.
   string16 composition_text_;
 
-  // |mouse_lock_owner_| is not owned by this class. We can know about when it
-  // is destroyed via InstanceDeleted().
-  // |mouse_lock_owner_| being non-NULL doesn't indicate that currently the
-  // mouse has been locked. It is possible that a request to lock the mouse has
-  // been sent, but the response hasn't arrived yet.
-  webkit::ppapi::PluginInstance* mouse_lock_owner_;
-  bool mouse_locked_;
-  // If both |pending_lock_request_| and |pending_unlock_request_| are true,
-  // it means a lock request was sent before an unlock request and we haven't
-  // received responses for them.
-  // The logic in LockMouse() makes sure that a lock request won't be sent when
-  // there is a pending unlock request.
-  bool pending_lock_request_;
-  bool pending_unlock_request_;
-
   // The plugin instance that received the last mouse event. It is set to NULL
   // if the last mouse event went to elements other than Pepper plugins.
   // |last_mouse_event_target_| is not owned by this class. We can know about
diff --git a/content/renderer/render_view_impl.cc b/content/renderer/render_view_impl.cc
index 99088a8..b76e2a8 100644
--- a/content/renderer/render_view_impl.cc
+++ b/content/renderer/render_view_impl.cc
@@ -64,6 +64,7 @@
 #include "content/renderer/media/media_stream_impl.h"
 #include "content/renderer/media/render_media_log.h"
 #include "content/renderer/mhtml_generator.h"
+#include "content/renderer/mouse_lock_dispatcher.h"
 #include "content/renderer/notification_provider.h"
 #include "content/renderer/p2p/socket_dispatcher.h"
 #include "content/renderer/plugin_channel_host.h"
@@ -335,6 +336,36 @@ struct RenderViewImpl::PendingFileChooser {
   WebFileChooserCompletion* completion;  // MAY BE NULL to skip callback.
 };
 
+namespace {
+
+class WebWidgetLockTarget : public MouseLockDispatcher::LockTarget {
+ public:
+  WebWidgetLockTarget (WebKit::WebWidget* webwidget)
+      : webwidget_(webwidget) {}
+
+  virtual void OnLockMouseACK(bool succeeded) OVERRIDE {
+    if (succeeded)
+      webwidget_->didAcquirePointerLock();
+    else
+      webwidget_->didNotAcquirePointerLock();
+  }
+
+  virtual void OnMouseLockLost() OVERRIDE {
+    webwidget_->didLosePointerLock();
+  }
+
+  virtual bool HandleMouseLockedInputEvent(
+      const WebKit::WebMouseEvent &event) OVERRIDE {
+    // The WebWidget handles mouse lock in WebKit's handleInputEvent().
+    return false;
+  }
+
+ private:
+  WebKit::WebWidget* webwidget_;
+};
+
+}  // namespace
+
 RenderViewImpl::RenderViewImpl(
     gfx::NativeViewId parent_hwnd,
     int32 opener_id,
@@ -374,6 +405,7 @@ RenderViewImpl::RenderViewImpl(
       p2p_socket_dispatcher_(NULL),
       devtools_agent_(NULL),
       renderer_accessibility_(NULL),
+      mouse_lock_dispatcher_(NULL),
       session_storage_namespace_id_(session_storage_namespace_id),
       handling_select_range_(false),
 #if defined(OS_WIN)
@@ -395,6 +427,7 @@ RenderViewImpl::RenderViewImpl(
 #endif
 
   webwidget_ = WebView::create(this);
+  webwidget_mouse_lock_target_.reset(new WebWidgetLockTarget(webwidget_));
 
   if (counter) {
     shared_popup_counter_ = counter;
@@ -445,9 +478,11 @@ RenderViewImpl::RenderViewImpl(
   new TextInputClientObserver(this);
 #endif  // defined(OS_MACOSX)
 
+  // The next group of objects all implement RenderViewObserver, so are deleted
+  // along with the RenderView automatically.
   devtools_agent_ = new DevToolsAgent(this);
-
   renderer_accessibility_ = new RendererAccessibility(this);
+  mouse_lock_dispatcher_ = new MouseLockDispatcher(this);
 
   new IdleUserDetector(this);
 
@@ -723,8 +758,6 @@ bool RenderViewImpl::OnMessageReceived(const IPC::Message& message) {
     IPC_MESSAGE_HANDLER(ViewMsg_SetHistoryLengthAndPrune,
                         OnSetHistoryLengthAndPrune)
     IPC_MESSAGE_HANDLER(ViewMsg_EnableViewSourceMode, OnEnableViewSourceMode)
-    IPC_MESSAGE_HANDLER(ViewMsg_LockMouse_ACK, OnLockMouseACK)
-    IPC_MESSAGE_HANDLER(ViewMsg_MouseLockLost, OnMouseLockLost)
     IPC_MESSAGE_HANDLER(JavaBridgeMsg_Init, OnJavaBridgeInit)
 
     // Have the super handle all other messages.
@@ -1928,6 +1961,19 @@ void RenderViewImpl::exitFullScreen() {
   Send(new ViewHostMsg_ToggleFullscreen(routing_id_, false));
 }
 
+bool RenderViewImpl::requestPointerLock() {
+  return mouse_lock_dispatcher_->LockMouse(webwidget_mouse_lock_target_.get());
+}
+
+void RenderViewImpl::requestPointerUnlock() {
+  mouse_lock_dispatcher_->UnlockMouse(webwidget_mouse_lock_target_.get());
+}
+
+bool RenderViewImpl::isPointerLocked() {
+  return mouse_lock_dispatcher_->IsMouseLockedTo(
+      webwidget_mouse_lock_target_.get());
+}
+
 // WebKit::WebFrameClient -----------------------------------------------------
 
 WebPlugin* RenderViewImpl::createPlugin(WebFrame* frame,
@@ -4386,7 +4432,11 @@ void RenderViewImpl::DidHandleKeyEvent() {
 }
 
 bool RenderViewImpl::WillHandleMouseEvent(const WebKit::WebMouseEvent& event) {
-  return pepper_delegate_.HandleMouseEvent(event);
+  pepper_delegate_.WillHandleMouseEvent();
+
+  // If the mouse is locked, only the current owner of the mouse lock can
+  // process mouse events.
+  return mouse_lock_dispatcher_->WillHandleMouseEvent(event);
 }
 
 void RenderViewImpl::DidHandleMouseEvent(const WebKit::WebMouseEvent& event) {
@@ -4895,23 +4945,6 @@ void RenderViewImpl::OnEnableViewSourceMode() {
   main_frame->enableViewSourceMode(true);
 }
 
-void RenderViewImpl::OnLockMouseACK(bool succeeded) {
-  // Mouse Lock removes the system cursor and provides all mouse motion as
-  // .movementX/Y values on events all sent to a fixed target. This requires
-  // content to specifically request the mode to be entered.
-  // Mouse Capture is implicitly given for the duration of a drag event, and
-  // sends all mouse events to the initial target of the drag.
-  // If Lock is entered it supercedes any in progress Capture.
-  if (succeeded)
-    OnMouseCaptureLost();
-
-  pepper_delegate_.OnLockMouseACK(succeeded);
-}
-
-void RenderViewImpl::OnMouseLockLost() {
-  pepper_delegate_.OnMouseLockLost();
-}
-
 bool RenderViewImpl::WebWidgetHandlesCompositorScheduling() const {
   return !!RenderThreadImpl::current()->compositor_thread();
 }
diff --git a/content/renderer/render_view_impl.h b/content/renderer/render_view_impl.h
index cf82759..e8728f4 100644
--- a/content/renderer/render_view_impl.h
+++ b/content/renderer/render_view_impl.h
@@ -67,6 +67,7 @@ class JavaBridgeDispatcher;
 class LoadProgressTracker;
 class MediaStreamDispatcher;
 class MediaStreamImpl;
+class MouseLockDispatcher;
 class NotificationProvider;
 class PepperDeviceTest;
 struct PP_NetAddress_Private;
@@ -213,6 +214,10 @@ class RenderViewImpl : public RenderWidget,
     return p2p_socket_dispatcher_;
   }
 
+  MouseLockDispatcher* mouse_lock_dispatcher() {
+    return mouse_lock_dispatcher_;
+  }
+
   WebKit::WebPeerConnectionHandler* CreatePeerConnectionHandler(
       WebKit::WebPeerConnectionHandlerClient* client);
 
@@ -317,6 +322,9 @@ class RenderViewImpl : public RenderWidget,
   virtual void runModal();
   virtual bool enterFullScreen();
   virtual void exitFullScreen();
+  virtual bool requestPointerLock();
+  virtual void requestPointerUnlock();
+  virtual bool isPointerLocked();
 
   // WebKit::WebViewClient implementation --------------------------------------
 
@@ -810,12 +818,10 @@ class RenderViewImpl : public RenderWidget,
       const std::vector<GURL>& links,
       const std::vector<FilePath>& local_paths,
       const FilePath& local_directory_name);
-  void OnLockMouseACK(bool succeeded);
   void OnMediaPlayerActionAt(const gfx::Point& location,
                              const WebKit::WebMediaPlayerAction& action);
   void OnPluginActionAt(const gfx::Point& location,
                         const WebKit::WebPluginAction& action);
-  void OnMouseLockLost();
   void OnMoveOrResizeStarted();
   CONTENT_EXPORT void OnNavigate(const ViewMsg_Navigate_Params& params);
   void OnPaste();
@@ -1168,6 +1174,9 @@ class RenderViewImpl : public RenderWidget,
   // Java Bridge dispatcher attached to this view; lazily initialized.
   scoped_ptr<JavaBridgeDispatcher> java_bridge_dispatcher_;
 
+  // Mouse Lock dispatcher attached to this view.
+  MouseLockDispatcher* mouse_lock_dispatcher_;
+
   // Misc ----------------------------------------------------------------------
 
   // The current and pending file chooser completion objects. If the queue is
@@ -1226,6 +1235,9 @@ class RenderViewImpl : public RenderWidget,
   // of handling a ViewMsg_SelectRange IPC.
   bool handling_select_range_;
 
+  // Wraps the |webwidget_| as a MouseLockDispatcher::LockTarget interface.
+  scoped_ptr<MouseLockDispatcher::LockTarget> webwidget_mouse_lock_target_;
+
   // Plugins -------------------------------------------------------------------
 
   // All the currently active plugin delegates for this RenderView; kept so
diff --git a/ppapi/examples/mouse_lock/mouse_lock.cc b/ppapi/examples/mouse_lock/mouse_lock.cc
index 6a934ba..f6bfbb6 100644
--- a/ppapi/examples/mouse_lock/mouse_lock.cc
+++ b/ppapi/examples/mouse_lock/mouse_lock.cc
@@ -1,4 +1,4 @@
-// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
@@ -75,8 +75,9 @@ class MyInstance : public pp::Instance, public pp::MouseLock {
             LockMouse(callback_factory_.NewRequiredCallback(
                 &MyInstance::DidLockMouse));
           }
+          return true;
         }
-        return true;
+        return false;
       }
       default:
         return false;
diff --git a/ppapi/examples/mouse_lock/mouse_lock.html b/ppapi/examples/mouse_lock/mouse_lock.html
index 5ce2261..5f0e5aa 100644
--- a/ppapi/examples/mouse_lock/mouse_lock.html
+++ b/ppapi/examples/mouse_lock/mouse_lock.html
@@ -1,7 +1,7 @@
 <!DOCTYPE html>
 <html>
   <!--
-  Copyright (c) 2011 The Chromium Authors. All rights reserved.
+  Copyright (c) 2012 The Chromium Authors. All rights reserved.
   Use of this source code is governed by a BSD-style license that can be
   found in the LICENSE file.
   -->
@@ -13,16 +13,6 @@
       height: 100%;
     }
   </style>
-  <script>
-    function ToggleFullscreen() {
-      if (document.webkitIsFullScreen) {
-        document.webkitCancelFullScreen();
-      } else {
-        document.getElementById('container').webkitRequestFullScreen(
-            Element.ALLOW_KEYBOARD_INPUT);
-      }
-    }
-  </script>
 </head>
 <body title="This tooltip should not be shown if the mouse is locked.">
 <div id="container">
@@ -61,15 +51,45 @@
     </li>
   </ul>
   <div>
-    <button id="toggle_fullscreen" onclick="ToggleFullscreen();">
+    <button onclick="ToggleFullscreen();">
       Toggle Tab Fullscreen
     </button>
+    <button onclick="AddAPlugin();">
+      Add A Plugin
+    </button>
+    <button onclick="RemoveAPlugin();">
+      Remove A Plugin (press 'x')
+    </button>
+  </div>
+  <div id="plugins_container">
   </div>
-  <object id="plugin" type="application/x-ppapi-example-mouse-lock"
-      width="300" height="300" border="2px"></object>
-  <div></div>
-  <object id="plugin" type="application/x-ppapi-example-mouse-lock"
-      width="300" height="300" border="2px"></object>
 </div>
 </body>
+<script>
+  plugins_container = document.getElementById("plugins_container");
+  AddAPlugin();
+  AddAPlugin();
+
+  function ToggleFullscreen() {
+    if (document.webkitIsFullScreen) {
+      document.webkitCancelFullScreen();
+    } else {
+      document.getElementById('container').webkitRequestFullScreen(
+          Element.ALLOW_KEYBOARD_INPUT);
+    }
+  }
+  function AddAPlugin() {
+    plugins_container.insertAdjacentHTML("BeforeEnd",
+        '<object type="application/x-ppapi-example-mouse-lock" ' +
+        'width="300" height="300" border="2px"></object>');
+  }
+  function RemoveAPlugin() {
+    if (plugins_container.firstElementChild)
+      plugins_container.removeChild(plugins_container.firstElementChild);
+  }
+  document.body.onkeydown = function (e) {
+    if (String.fromCharCode(e.keyCode) == "X")
+      RemoveAPlugin();
+  }
+</script>
 </html>
diff --git a/webkit/plugins/ppapi/mock_plugin_delegate.cc b/webkit/plugins/ppapi/mock_plugin_delegate.cc
index da371c54..780bf4c 100644
--- a/webkit/plugins/ppapi/mock_plugin_delegate.cc
+++ b/webkit/plugins/ppapi/mock_plugin_delegate.cc
@@ -348,13 +348,17 @@ base::SharedMemory* MockPluginDelegate::CreateAnonymousSharedMemory(
   return ::ppapi::Preferences();
 }
 
-void MockPluginDelegate::LockMouse(PluginInstance* instance) {
-  instance->OnLockMouseACK(PP_ERROR_FAILED);
+bool MockPluginDelegate::LockMouse(PluginInstance* instance) {
+  return false;
 }
 
 void MockPluginDelegate::UnlockMouse(PluginInstance* instance) {
 }
 
+bool MockPluginDelegate::IsMouseLocked(PluginInstance* instance) {
+  return false;
+}
+
 void MockPluginDelegate::DidChangeCursor(PluginInstance* instance,
                                          const WebKit::WebCursorInfo& cursor) {
 }
diff --git a/webkit/plugins/ppapi/mock_plugin_delegate.h b/webkit/plugins/ppapi/mock_plugin_delegate.h
index fbd961a..4768080 100644
--- a/webkit/plugins/ppapi/mock_plugin_delegate.h
+++ b/webkit/plugins/ppapi/mock_plugin_delegate.h
@@ -148,8 +148,9 @@ class MockPluginDelegate : public PluginDelegate {
   virtual std::string GetFlashCommandLineArgs();
   virtual base::SharedMemory* CreateAnonymousSharedMemory(uint32_t size);
   virtual ::ppapi::Preferences GetPreferences();
-  virtual void LockMouse(PluginInstance* instance);
+  virtual bool LockMouse(PluginInstance* instance);
   virtual void UnlockMouse(PluginInstance* instance);
+  virtual bool IsMouseLocked(PluginInstance* instance);
   virtual void DidChangeCursor(PluginInstance* instance,
                                const WebKit::WebCursorInfo& cursor);
   virtual void DidReceiveMouseEvent(PluginInstance* instance);
diff --git a/webkit/plugins/ppapi/plugin_delegate.h b/webkit/plugins/ppapi/plugin_delegate.h
index 6f9a17e..d91621c 100644
--- a/webkit/plugins/ppapi/plugin_delegate.h
+++ b/webkit/plugins/ppapi/plugin_delegate.h
@@ -490,11 +490,11 @@ class PluginDelegate {
   // Returns the current preferences.
   virtual ::ppapi::Preferences GetPreferences() = 0;
 
-  // Locks the mouse for |instance|. It will call
-  // PluginInstance::OnLockMouseACK() to notify the instance when the operation
-  // is completed. The call to OnLockMouseACK() may be synchronous (i.e., it may
-  // be called when LockMouse() is still on the stack).
-  virtual void LockMouse(PluginInstance* instance) = 0;
+  // Locks the mouse for |instance|. If false is returned, the lock is not
+  // possible. If true is returned then the lock is pending. Success or
+  // failure will be delivered asynchronously via
+  // PluginInstance::OnLockMouseACK().
+  virtual bool LockMouse(PluginInstance* instance) = 0;
 
   // Unlocks the mouse if |instance| currently owns the mouse lock. Whenever an
   // plugin instance has lost the mouse lock, it will be notified by
@@ -504,6 +504,9 @@ class PluginDelegate {
   // call to the current mouse lock owner.
   virtual void UnlockMouse(PluginInstance* instance) = 0;
 
+  // Returns true iff |instance| currently owns the mouse lock.
+  virtual bool IsMouseLocked(PluginInstance* instance) = 0;
+
   // Notifies that |instance| has changed the cursor.
   // This will update the cursor appearance if it is currently over the plugin
   // instance.
diff --git a/webkit/plugins/ppapi/ppapi_plugin_instance.cc b/webkit/plugins/ppapi/ppapi_plugin_instance.cc
index 7f849f6..23a1862 100644
--- a/webkit/plugins/ppapi/ppapi_plugin_instance.cc
+++ b/webkit/plugins/ppapi/ppapi_plugin_instance.cc
@@ -1675,13 +1675,13 @@ bool PluginInstance::IsFullPagePlugin() const {
   return frame->view()->mainFrame()->document().isPluginDocument();
 }
 
-void PluginInstance::OnLockMouseACK(int32_t result) {
+void PluginInstance::OnLockMouseACK(bool succeeded) {
   if (!lock_mouse_callback_.func) {
     NOTREACHED();
     return;
   }
-
-  PP_RunAndClearCompletionCallback(&lock_mouse_callback_, result);
+  PP_RunAndClearCompletionCallback(&lock_mouse_callback_,
+                                   succeeded ? PP_OK : PP_ERROR_FAILED);
 }
 
 void PluginInstance::OnMouseLockLost() {
@@ -1689,6 +1689,13 @@ void PluginInstance::OnMouseLockLost() {
     plugin_mouse_lock_interface_->MouseLockLost(pp_instance());
 }
 
+void PluginInstance::HandleMouseLockedInputEvent(
+    const WebKit::WebMouseEvent& event) {
+  // |cursor_info| is ignored since it is hidden when the mouse is locked.
+  WebKit::WebCursorInfo cursor_info;
+  HandleInputEvent(event, &cursor_info);
+}
+
 void PluginInstance::SimulateInputEvent(const InputEventData& input_event) {
   WebView* web_view = container()->element().document().frame()->view();
   if (!web_view) {
@@ -1974,16 +1981,21 @@ int32_t PluginInstance::LockMouse(PP_Instance instance,
     // Don't support synchronous call.
     return PP_ERROR_BLOCKS_MAIN_THREAD;
   }
-  if (lock_mouse_callback_.func)
+  if (lock_mouse_callback_.func)  // A lock is pending.
     return PP_ERROR_INPROGRESS;
+
+  if (delegate()->IsMouseLocked(this))
+    return PP_OK;
+
   if (!CanAccessMainFrame())
     return PP_ERROR_NOACCESS;
 
-  lock_mouse_callback_ = callback;
-  // We will be notified on completion via OnLockMouseACK(), either
-  // synchronously or asynchronously.
-  delegate()->LockMouse(this);
-  return PP_OK_COMPLETIONPENDING;
+  if (delegate()->LockMouse(this)) {
+    lock_mouse_callback_ = callback;
+    return PP_OK_COMPLETIONPENDING;
+  } else {
+    return PP_ERROR_FAILED;
+  }
 }
 
 void PluginInstance::UnlockMouse(PP_Instance instance) {
diff --git a/webkit/plugins/ppapi/ppapi_plugin_instance.h b/webkit/plugins/ppapi/ppapi_plugin_instance.h
index 086125f..c8a6332 100644
--- a/webkit/plugins/ppapi/ppapi_plugin_instance.h
+++ b/webkit/plugins/ppapi/ppapi_plugin_instance.h
@@ -52,6 +52,7 @@ class TransportDIB;
 
 namespace WebKit {
 class WebInputEvent;
+class WebMouseEvent;
 class WebPluginContainer;
 struct WebCompositionUnderline;
 struct WebCursorInfo;
@@ -305,8 +306,12 @@ class WEBKIT_PLUGINS_EXPORT PluginInstance :
   // or embedded in a page).
   bool IsFullPagePlugin() const;
 
-  void OnLockMouseACK(int32_t result);
+  // A mouse lock request was pending and this reports success or failure.
+  void OnLockMouseACK(bool succeeded);
+  // A mouse lock was in place, but has been lost.
   void OnMouseLockLost();
+  // A mouse lock is enabled and mouse events are being delievered.
+  void HandleMouseLockedInputEvent(const WebKit::WebMouseEvent& event);
 
   // Simulates an input event to the plugin by passing it down to WebKit,
   // which sends it back up to the plugin as if it came from the user.