Make cc::CompositorFrames movable [Part 1 of 2]

content/public/browser/android/synchronous_compositor.h

Index: content/public/browser/android/synchronous_compositor.h
diff --git a/content/public/browser/android/synchronous_compositor.h b/content/public/browser/android/synchronous_compositor.h
index bc74f1f240f12212fcee1f449591c2b06f62fd6b..c5dd759184ec35b999d588815267ad081c9b073d 100644
--- a/content/public/browser/android/synchronous_compositor.h
+++ b/content/public/browser/android/synchronous_compositor.h
@@ -10,7 +10,9 @@
 #include <memory>
 
 #include "base/memory/ref_counted.h"
+#include "base/optional.h"
 #include "base/time/time.h"
+#include "cc/output/compositor_frame.h"
 #include "content/common/content_export.h"
 #include "ui/gfx/geometry/rect.h"
 #include "ui/gfx/geometry/size.h"
@@ -18,7 +20,6 @@
 class SkCanvas;
 
 namespace cc {
-class CompositorFrame;
 class CompositorFrameAck;
 }
 
@@ -52,7 +53,7 @@ class CONTENT_EXPORT SynchronousCompositor {
     Frame& operator=(Frame&& rhs);
 
     uint32_t output_surface_id;
-    std::unique_ptr<cc::CompositorFrame> frame;
+    base::Optional<cc::CompositorFrame> frame;
 
    private:
     DISALLOW_COPY_AND_ASSIGN(Frame);