Added FrameFuture class

content/public/browser/android/synchronous_compositor.cc

Index: content/public/browser/android/synchronous_compositor.cc
diff --git a/content/public/browser/android/synchronous_compositor.cc b/content/public/browser/android/synchronous_compositor.cc
index 4e52b6130c4a37269f351cdced838b4b55b64d72..84869dc44c5e25f9376e6f956ee2708189b463a2 100644
--- a/content/public/browser/android/synchronous_compositor.cc
+++ b/content/public/browser/android/synchronous_compositor.cc
@@ -17,6 +17,28 @@ SynchronousCompositor::Frame::~Frame() {}
 SynchronousCompositor::Frame::Frame(Frame&& rhs)
     : output_surface_id(rhs.output_surface_id), frame(std::move(rhs.frame)) {}
 
+SynchronousCompositor::FrameFuture::FrameFuture()
+    : waitable_event_(base::WaitableEvent::ResetPolicy::AUTOMATIC,

[boliu, 2016/09/16 16:26:12]

should be manual

[ojars, 2016/09/19 22:02:37]

Done.

+                      base::WaitableEvent::InitialState::NOT_SIGNALED) {}
+
+SynchronousCompositor::FrameFuture::~FrameFuture() {}
+
+void SynchronousCompositor::FrameFuture::setFrame(
+    std::unique_ptr<content::SynchronousCompositor::Frame> frame) {
+  frame_ = std::move(frame);
+  waitable_event_.Signal();
+}
+
+content::SynchronousCompositor::Frame*
+SynchronousCompositor::FrameFuture::getFrame() {
+  waitable_event_.Wait();

[boliu, 2016/09/16 16:26:12]

All the waitable_event calls are super expensive. We shouldn't repeat the just
because all over the place.

Hmm, this is actually an interesting exercise how this class should behave. I
think we should talk about this in person.

+  return frame_.get();
+}
+
+bool SynchronousCompositor::FrameFuture::hasFrame() {
+  return waitable_event_.IsSignaled();
+}
+
 SynchronousCompositor::Frame& SynchronousCompositor::Frame::operator=(
     Frame&& rhs) {
   output_surface_id = rhs.output_surface_id;