7 files changed, 29 insertions, 4 deletions
diff --git a/chrome/test/ppapi/ppapi_test.cc b/chrome/test/ppapi/ppapi_test.cc
index 0728fc0..5da65af 100644
--- a/chrome/test/ppapi/ppapi_test.cc
+++ b/chrome/test/ppapi/ppapi_test.cc
@@ -133,6 +133,9 @@ void PPAPITestBase::SetUpCommandLine(CommandLine* command_line) {
 
   // Smooth scrolling confuses the scrollbar test.
   command_line->AppendSwitch(switches::kDisableSmoothScrolling);
+
+  // Enable threading since we test that feature.
+  command_line->AppendSwitch(switches::kEnablePepperThreading);
 }
 
 void PPAPITestBase::SetUpOnMainThread() {
diff --git a/content/browser/ppapi_plugin_process_host.cc b/content/browser/ppapi_plugin_process_host.cc
index e064e7d..e333ff0 100644
--- a/content/browser/ppapi_plugin_process_host.cc
+++ b/content/browser/ppapi_plugin_process_host.cc
@@ -237,6 +237,7 @@ bool PpapiPluginProcessHost::Init(const PepperPluginInfo& info) {
     // going to explode.
     static const char* kPluginForwardSwitches[] = {
       switches::kDisableSeccompFilterSandbox,
+      switches::kEnablePepperThreading,
 #if defined(OS_MACOSX)
       switches::kEnableSandboxLogging,
 #endif
diff --git a/content/ppapi_plugin/ppapi_thread.cc b/content/ppapi_plugin/ppapi_thread.cc
index 7ee63f6..782f804 100644
--- a/content/ppapi_plugin/ppapi_thread.cc
+++ b/content/ppapi_plugin/ppapi_thread.cc
@@ -61,6 +61,8 @@ PpapiThread::PpapiThread(const CommandLine& command_line, bool is_broker)
   globals->set_plugin_proxy_delegate(this);
   globals->set_command_line(
       command_line.GetSwitchValueASCII(switches::kPpapiFlashArgs));
+  globals->set_enable_threading(
+      command_line.HasSwitch(switches::kEnablePepperThreading));
 
   webkit_platform_support_.reset(new PpapiWebKitPlatformSupportImpl);
   WebKit::initialize(webkit_platform_support_.get());
diff --git a/ppapi/proxy/plugin_globals.cc b/ppapi/proxy/plugin_globals.cc
index 75369d0..79e7383 100644
--- a/ppapi/proxy/plugin_globals.cc
+++ b/ppapi/proxy/plugin_globals.cc
@@ -20,6 +20,12 @@ PluginGlobals::PluginGlobals()
       callback_tracker_(new CallbackTracker),
       loop_for_main_thread_(
           new MessageLoopResource(MessageLoopResource::ForMainThread())) {
+#if defined(ENABLE_PEPPER_THREADING)
+  enable_threading_ = true;
+#else
+  enable_threading_ = false;
+#endif
+
   DCHECK(!plugin_globals_);
   plugin_globals_ = this;
 }
@@ -28,6 +34,11 @@ PluginGlobals::PluginGlobals(ForTest for_test)
     : ppapi::PpapiGlobals(for_test),
       plugin_proxy_delegate_(NULL),
       callback_tracker_(new CallbackTracker) {
+#if defined(ENABLE_PEPPER_THREADING)
+  enable_threading_ = true;
+#else
+  enable_threading_ = false;
+#endif
   DCHECK(!plugin_globals_);
 }
 
@@ -80,11 +91,9 @@ void PluginGlobals::PreCacheFontForFlash(const void* logfontw) {
 }
 
 base::Lock* PluginGlobals::GetProxyLock() {
-#ifdef ENABLE_PEPPER_THREADING
-  return &proxy_lock_;
-#else
+  if (enable_threading_)
+    return &proxy_lock_;
   return NULL;
-#endif
 }
 
 void PluginGlobals::LogWithSource(PP_Instance instance,
diff --git a/ppapi/proxy/plugin_globals.h b/ppapi/proxy/plugin_globals.h
index 215ad63..c8bf113 100644
--- a/ppapi/proxy/plugin_globals.h
+++ b/ppapi/proxy/plugin_globals.h
@@ -100,6 +100,10 @@ class PPAPI_PROXY_EXPORT PluginGlobals : public PpapiGlobals {
   // The embedder should call this function when the command line is known.
   void set_command_line(const std::string& c) { command_line_ = c; }
 
+  // Sets whether threadsafety is supported. Defaults to whether the
+  // ENABLE_PEPPER_THREADING build flag is set.
+  void set_enable_threading(bool enable) { enable_threading_ = enable; }
+
  private:
   // PpapiGlobals overrides.
   virtual bool IsPluginGlobals() const OVERRIDE;
@@ -110,6 +114,8 @@ class PPAPI_PROXY_EXPORT PluginGlobals : public PpapiGlobals {
   PluginResourceTracker plugin_resource_tracker_;
   PluginVarTracker plugin_var_tracker_;
   scoped_refptr<CallbackTracker> callback_tracker_;
+
+  bool enable_threading_;  // Indicates whether we'll use the lock.
   base::Lock proxy_lock_;
 
   scoped_ptr<base::ThreadLocalStorage::Slot> msg_loop_slot_;
diff --git a/webkit/plugins/plugin_switches.cc b/webkit/plugins/plugin_switches.cc
index bb1b3b4..98a43c2 100644
--- a/webkit/plugins/plugin_switches.cc
+++ b/webkit/plugins/plugin_switches.cc
@@ -15,6 +15,9 @@ const char kDisablePepper3d[] = "disable-pepper-3d";
 // "Command-line" arguments for the PPAPI Flash; used for debugging options.
 const char kPpapiFlashArgs[] = "ppapi-flash-args";
 
+// Set to true to allow threadsafety support in native Pepper plugins.
+const char kEnablePepperThreading[] = "enable-pepper-threading";
+
 #if defined(OS_WIN)
 // Used by the plugins_test when testing the older WMP plugin to force the new
 // plugin to not get loaded.
diff --git a/webkit/plugins/plugin_switches.h b/webkit/plugins/plugin_switches.h
index 08ed5ae..ac3a8c5 100644
--- a/webkit/plugins/plugin_switches.h
+++ b/webkit/plugins/plugin_switches.h
@@ -13,6 +13,7 @@ namespace switches {
 WEBKIT_PLUGINS_EXPORT extern const char kDebugPluginLoading[];
 WEBKIT_PLUGINS_EXPORT extern const char kDisablePepper3d[];
 WEBKIT_PLUGINS_EXPORT extern const char kPpapiFlashArgs[];
+WEBKIT_PLUGINS_EXPORT extern const char kEnablePepperThreading[];
 
 #if defined(OS_WIN)
 WEBKIT_PLUGINS_EXPORT extern const char kUseOldWMPPlugin[];