Bug 1150944 - Don't force the discrete GPU for skia gl. r=jrmuizel

gfx/gl/GLContextProvider.h

@@ -23,6 +23,8 @@ enum class CreateContextFlags : int8_t {
     REQUIRE_COMPAT_PROFILE = 1 << 0,
     // Force the use of hardware backed GL, don't allow software implementations.
     FORCE_ENABLE_HARDWARE = 1 << 1,
+    /* Don't force discrete GPU to be used (if applicable) */
+    ALLOW_OFFLINE_RENDERER =  1 << 2,
 };
 MOZ_MAKE_ENUM_CLASS_BITWISE_OPERATORS(CreateContextFlags)
 

gfx/gl/GLContextProviderCGL.mm

@@ -187,6 +187,11 @@ static const NSOpenGLPixelFormatAttribute kAttribs_offscreen[] = {
     0
 };
 
+static const NSOpenGLPixelFormatAttribute kAttribs_offscreen_allow_offline[] = {
+    NSOpenGLPFAAllowOfflineRenderers,
+    0
+};
+
 static const NSOpenGLPixelFormatAttribute kAttribs_offscreen_accel[] = {
     NSOpenGLPFAAccelerated,
     0
@@ -269,10 +274,18 @@ CreateOffscreenFBOContext(CreateContextFlags flags)
     if (!context) {
         profile = ContextProfile::OpenGLCompatibility;
 
-        if (gfxPrefs::RequireHardwareGL())
-            context = CreateWithFormat(kAttribs_offscreen_accel);
-        else
-            context = CreateWithFormat(kAttribs_offscreen);
+        if (flags & CreateContextFlags::ALLOW_OFFLINE_RENDERER) {
+          if (gfxPrefs::RequireHardwareGL())
+              context = CreateWithFormat(kAttribs_singleBuffered);
+          else
+              context = CreateWithFormat(kAttribs_offscreen_allow_offline);
+
+        } else {
+          if (gfxPrefs::RequireHardwareGL())
+              context = CreateWithFormat(kAttribs_offscreen_accel);
+          else
+              context = CreateWithFormat(kAttribs_offscreen);
+        }
     }
     if (!context) {
         NS_WARNING("Failed to create NSOpenGLContext.");

gfx/thebes/gfxPlatform.cpp

@@ -1090,7 +1090,8 @@ gfxPlatform::GetSkiaGLGlue()
      * stands, this only works on the main thread.
      */
     nsRefPtr<GLContext> glContext;
-    glContext = GLContextProvider::CreateHeadless(CreateContextFlags::REQUIRE_COMPAT_PROFILE);
+    glContext = GLContextProvider::CreateHeadless(CreateContextFlags::REQUIRE_COMPAT_PROFILE |
+                                                  CreateContextFlags::ALLOW_OFFLINE_RENDERER);
     if (!glContext) {
       printf_stderr("Failed to create GLContext for SkiaGL!\n");
       return nullptr;