Preempt renderers by browser UI in GpuScheduler.

Adds a message filter in GpuChannel to detect if the UI has commands to execute. This is polled in GpuScheduler so that renderers will defer to the UI.

BUG=none
TEST=smoothly drag a window of https://cvs.khronos.org/svn/repos/registry/trunk/public/webgl/sdk/demos/google/san-angeles/index.html on alex

Review URL: https://chromiumcodereview.appspot.com/10186002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@140866 0039d316-1c4b-4281-b951-d872f2087c98

3 files changed, 42 insertions, 2 deletions

diff --git a/gpu/command_buffer/service/gpu_scheduler.cc b/gpu/command_buffer/service/gpu_scheduler.cc
index af34f76..85d4f75 100644
--- a/gpu/command_buffer/service/gpu_scheduler.cc
+++ b/gpu/command_buffer/service/gpu_scheduler.cc
@@ -32,7 +32,8 @@ GpuScheduler::GpuScheduler(
       parser_(NULL),
       unscheduled_count_(0),
       rescheduled_count_(0),
-      reschedule_task_factory_(ALLOW_THIS_IN_INITIALIZER_LIST(this)) {
+      reschedule_task_factory_(ALLOW_THIS_IN_INITIALIZER_LIST(this)),
+      was_preempted_(false) {
 }
 
 GpuScheduler::~GpuScheduler() {
@@ -63,6 +64,17 @@ void GpuScheduler::PutChanged() {
 
   error::Error error = error::kNoError;
   while (!parser_->IsEmpty()) {
+    if (preempt_by_counter_.get() &&
+        !was_preempted_ &&
+        !preempt_by_counter_->IsZero()) {
+      TRACE_COUNTER_ID1("gpu","GpuScheduler::Preempted", this, 1);
+      was_preempted_ = true;
+      return;
+    } else if (was_preempted_) {
+      TRACE_COUNTER_ID1("gpu","GpuScheduler::Preempted", this, 0);
+      was_preempted_ = false;
+    }
+
     DCHECK(IsScheduled());
     DCHECK(unschedule_fences_.empty());
 
diff --git a/gpu/command_buffer/service/gpu_scheduler.h b/gpu/command_buffer/service/gpu_scheduler.h
index 2ae048b..9aa7d9e 100644
--- a/gpu/command_buffer/service/gpu_scheduler.h
+++ b/gpu/command_buffer/service/gpu_scheduler.h
@@ -7,9 +7,12 @@
 
 #include <queue>
 
+#include "base/atomicops.h"
+#include "base/atomic_ref_count.h"
 #include "base/callback.h"
-#include "base/memory/scoped_ptr.h"
 #include "base/memory/linked_ptr.h"
+#include "base/memory/ref_counted.h"
+#include "base/memory/scoped_ptr.h"
 #include "base/memory/weak_ptr.h"
 #include "base/shared_memory.h"
 #include "gpu/command_buffer/common/command_buffer.h"
@@ -24,6 +27,21 @@ class GLFence;
 
 namespace gpu {
 
+struct RefCountedCounter
+    : public base::RefCountedThreadSafe<RefCountedCounter> {
+  base::AtomicRefCount count;
+  RefCountedCounter() : count(0) {}
+
+  bool IsZero() { return base::AtomicRefCountIsZero(&count); }
+  void IncCount() { base::AtomicRefCountInc(&count); }
+  void DecCount() { base::AtomicRefCountDec(&count); }
+  void Reset() { base::subtle::NoBarrier_Store(&count, 0); }
+ private:
+  ~RefCountedCounter() {}
+
+  friend class base::RefCountedThreadSafe<RefCountedCounter>;
+};
+
 // This class schedules commands that have been flushed. They are received via
 // a command buffer and forwarded to a command parser. TODO(apatrick): This
 // class should not know about the decoder. Do not add additional dependencies
@@ -40,6 +58,10 @@ class GPU_EXPORT GpuScheduler
 
   void PutChanged();
 
+  void SetPreemptByCounter(scoped_refptr<RefCountedCounter> counter) {
+    preempt_by_counter_ = counter;
+  }
+
   // Sets whether commands should be processed by this scheduler. Setting to
   // false unschedules. Setting to true reschedules. Whether or not the
   // scheduler is currently scheduled is "reference counted". Every call with
@@ -123,6 +145,11 @@ class GPU_EXPORT GpuScheduler
   base::Closure scheduled_callback_;
   base::Closure command_processed_callback_;
 
+  // If non-NULL and preempt_by_counter_->count is non-zero,
+  // exit PutChanged early.
+  scoped_refptr<RefCountedCounter> preempt_by_counter_;
+  bool was_preempted_;
+
   DISALLOW_COPY_AND_ASSIGN(GpuScheduler);
 };
 
diff --git a/gpu/command_buffer_service.gypi b/gpu/command_buffer_service.gypi
index 5e7d6a6..02bfaf6 100644
--- a/gpu/command_buffer_service.gypi
+++ b/gpu/command_buffer_service.gypi
@@ -15,6 +15,7 @@
   },
   'dependencies': [
     '../base/base.gyp:base',
+    '../base/third_party/dynamic_annotations/dynamic_annotations.gyp:dynamic_annotations',
     '../crypto/crypto.gyp:crypto',
     '../ui/gl/gl.gyp:gl',
     '../ui/surface/surface.gyp:surface',