Refactor GL surface format handling

ui/gl/init/gl_factory_mac.cc

Index: ui/gl/init/gl_factory_mac.cc
diff --git a/ui/gl/init/gl_factory_mac.cc b/ui/gl/init/gl_factory_mac.cc
index 243a7909b59e5ab9efa0e425a0a2079d6e55b868..1bcfbadd2e42d337b5e3201e8a2f9f4517eddc73 100644
--- a/ui/gl/init/gl_factory_mac.cc
+++ b/ui/gl/init/gl_factory_mac.cc
@@ -32,7 +32,7 @@ class NoOpGLSurface : public GLSurface {
   explicit NoOpGLSurface(const gfx::Size& size) : size_(size) {}
 
   // Implement GLSurface.
-  bool Initialize(GLSurface::Format format) override { return true; }
+  bool Initialize(GLSurfaceFormat format) override { return true; }
   void Destroy() override {}
   bool IsOffscreen() override { return true; }
   gfx::SwapResult SwapBuffers() override {
@@ -113,16 +113,19 @@ scoped_refptr<GLSurface> CreateViewGLSurface(gfx::AcceleratedWidget window) {
   }
 }
 
-scoped_refptr<GLSurface> CreateOffscreenGLSurface(const gfx::Size& size) {
+scoped_refptr<GLSurface> CreateOffscreenGLSurfaceWithFormat(
+    const gfx::Size& size, GLSurfaceFormat format) {
   TRACE_EVENT0("gpu", "gl::init::CreateOffscreenGLSurface");
   switch (GetGLImplementation()) {
     case kGLImplementationOSMesaGL:
-      return InitializeGLSurface(
-          new GLSurfaceOSMesa(GLSurface::SURFACE_OSMESA_RGBA, size));
+      format.SetDefaultPixelLayout(GLSurfaceFormat::PIXEL_LAYOUT_RGBA);
+      return InitializeGLSurfaceWithFormat(
+          new GLSurfaceOSMesa(format, size), format);
     case kGLImplementationDesktopGL:
     case kGLImplementationDesktopGLCoreProfile:
     case kGLImplementationAppleGL:
-      return InitializeGLSurface(new NoOpGLSurface(size));
+      return InitializeGLSurfaceWithFormat(
+          new NoOpGLSurface(size), format);
     case kGLImplementationMockGL:
       return new GLSurfaceStub;
     default: