Add timeout to swap fence

gpu/ipc/service/image_transport_surface_overlay_mac.mm

Index: gpu/ipc/service/image_transport_surface_overlay_mac.mm
diff --git a/gpu/ipc/service/image_transport_surface_overlay_mac.mm b/gpu/ipc/service/image_transport_surface_overlay_mac.mm
index 1ced5d09fe883c99e9e6531bd40af9c9056e4e24..f68ffc4623f330d6ad10718606b4bce0f3ff9ea6 100644
--- a/gpu/ipc/service/image_transport_surface_overlay_mac.mm
+++ b/gpu/ipc/service/image_transport_surface_overlay_mac.mm
@@ -182,10 +182,18 @@ gfx::SwapResult ImageTransportSurfaceOverlayMac::SwapBuffersInternal(
       // While we could call GLFence::ClientWait, this performs a busy wait on
       // Mac, leading to high CPU usage. Instead we poll with a 1ms delay. This
       // should have minimal impact, as we will only hit this path when we are
-      // more than one frame (16ms) behind.
-      while (!previous_frame_fence_->HasCompleted()) {
+      // more than one frame (16ms) behind. Note that on some platforms (10.9),
+      // fences appear to sometimes get lost and will naver pass. Add a 32ms

[ccameron, 2016/06/13 22:16:14]

s/naver/never

[ericrk, 2016/06/13 22:23:14]

Done.

+      // timout to prevent these situations from causing a GPU process hang.
+      int timeout = 32;

[ccameron, 2016/06/13 22:16:14]

s/timeout/timeout_msec

[ericrk, 2016/06/13 22:23:14]

Done.

+      while (!previous_frame_fence_->HasCompleted() && timeout > 0) {
+        --timeout;
         base::PlatformThread::Sleep(base::TimeDelta::FromMilliseconds(1));
       }
+      if (!previous_frame_fence_->HasCompleted()) {
+        // We timed out waiting for the above fence, just issue a glFinish.
+        glFinish();
+      }
     }
 
     // Create a fence for the current frame's work and save the context.