Add timeout to swap fence

gpu/ipc/service/image_transport_surface_overlay_mac.mm

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "gpu/ipc/service/image_transport_surface_overlay_mac.h"
 
 #include <CoreGraphics/CoreGraphics.h>
 #include <IOSurface/IOSurface.h>
 #include <OpenGL/CGLRenderers.h>
 #include <OpenGL/CGLTypes.h>
@@ skipping 164 matching lines @@
     // frame to complete.
     if (previous_frame_fence_) {
       TRACE_EVENT0("gpu", "ImageTransportSurfaceOverlayMac::ClientWait");
 
       // Ensure we are using the context with which the fence was created.
       gl::ScopedCGLSetCurrentContext scoped_set_current(fence_context_obj_);
 
       // 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.
     previous_frame_fence_.reset(gl::GLFence::Create());
     fence_context_obj_.reset(CGLGetCurrentContext(),
                              base::scoped_policy::RETAIN);
 
     // A glFlush is necessary to ensure correct content appears.
     glFlush();
 
@@ skipping 156 matching lines @@
   gl_renderer_id_ = context_renderer_id & kCGLRendererIDMatchingMask;
 
   // Post a task holding a reference to the new GL context. The reason for
   // this is to avoid creating-then-destroying the context for every image
   // transport surface that is observing the GPU switch.
   base::MessageLoop::current()->PostTask(
       FROM_HERE, base::Bind(&IOSurfaceContextNoOp, context_on_new_gpu));
 }
 
 }  // namespace gpu