Bug 888899: Allow fast iterations of the refresh driver on OS X. r=jrmuizel

gfx/gl/GLContextProviderCGL.mm

@@ -136,7 +136,12 @@ public:
 
         if (mContext) {
             [mContext makeCurrentContext];
-            GLint swapInt = 1;
+            // Use blocking swap only with the default frame rate.
+            // If swapInt is 1, then glSwapBuffers will block and wait for a vblank signal.
+            // While this is fine for the default refresh rate, if the user chooses some
+            // other rate, and specifically if this rate is higher than the screen refresh rate,
+            // then we want a non-blocking glSwapBuffers, which will happen when swapInt==0.
+            GLint swapInt = gfxPlatform::GetPrefLayoutFrameRate() == -1 ? 1 : 0;
             [mContext setValues:&swapInt forParameter:NSOpenGLCPSwapInterval];
         }
         return true;

gfx/thebes/gfxPlatform.cpp

@@ -1836,6 +1836,7 @@ static bool sPrefLayersAccelerationForceEnabled = false;
 static bool sPrefLayersAccelerationDisabled = false;
 static bool sPrefLayersPreferOpenGL = false;
 static bool sPrefLayersPreferD3D9 = false;
+static int  sPrefLayoutFrameRate = -1;
 
 void InitLayersAccelerationPrefs()
 {
@@ -1849,6 +1850,7 @@ void InitLayersAccelerationPrefs()
     sPrefLayersAccelerationDisabled = Preferences::GetBool("layers.acceleration.disabled", false);
     sPrefLayersPreferOpenGL = Preferences::GetBool("layers.prefer-opengl", false);
     sPrefLayersPreferD3D9 = Preferences::GetBool("layers.prefer-d3d9", false);
+    sPrefLayoutFrameRate = Preferences::GetInt("layout.frame_rate", -1);
 
     sLayersAccelerationPrefsInitialized = true;
   }
@@ -1892,3 +1894,9 @@ bool gfxPlatform::GetPrefLayersPreferD3D9()
   InitLayersAccelerationPrefs();
   return sPrefLayersPreferD3D9;
 }
+
+int gfxPlatform::GetPrefLayoutFrameRate()
+{
+  InitLayersAccelerationPrefs();
+  return sPrefLayoutFrameRate;
+}

gfx/thebes/gfxPlatform.h

@@ -467,6 +467,7 @@ public:
     static bool GetPrefLayersAccelerationDisabled();
     static bool GetPrefLayersPreferOpenGL();
     static bool GetPrefLayersPreferD3D9();
+    static int  GetPrefLayoutFrameRate();
 
     /**
      * Are we going to try color management?