gpu: Work around Mali-400 driver bug.

ui/gl/async_pixel_transfer_delegate_android.cc

 // Copyright (c) 2012 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 "ui/gl/async_pixel_transfer_delegate_android.h"
 
 #include <string>
 
 #include "base/bind.h"
 #include "base/debug/trace_event.h"
@@ skipping 203 matching lines @@
     // doing the first upload (or the texture remains black).
     // A fence after image creation didn't always work, but glFinish
     // seems to always work, and this only happens on the upload thread.
     if (wait_for_egl_images_) {
       TRACE_EVENT0("gpu", "glFinish");
       glFinish();
     }
   }
 
   void WaitForLastUpload() {
-    if (!wait_for_uploads_)
-      return;
-
-    // This fence is basically like calling glFinish, which is fine on
-    // the upload thread if uploads occur on the CPU. We may want to delay
-    // blocking on this fence if this causes any stalls.
-
-    TRACE_EVENT0("gpu", "eglWaitSync");
-    EGLDisplay display = eglGetCurrentDisplay();
-    EGLSyncKHR fence = eglCreateSyncKHR(display, EGL_SYNC_FENCE_KHR, NULL);
-    EGLint flags = EGL_SYNC_FLUSH_COMMANDS_BIT_KHR;
-    EGLTimeKHR time = EGL_FOREVER_KHR;
-    eglClientWaitSyncKHR(display, fence, flags, time);
-    eglDestroySyncKHR(display, fence);
+    // This glFinish is just a safe-guard for if uploads have some
+    // GPU action that needs to occur. We could use fences and try
+    // to do this less often. However, on older drivers fences are
+    // not always reliable (eg. Mali-400 just blocks forever).
+    if (wait_for_uploads_) {
+      TRACE_EVENT0("gpu", "glFinish");
+      glFinish();
+    }
   }
 
  protected:
   friend class base::RefCountedThreadSafe<TransferStateInternal>;
   friend class AsyncPixelTransferDelegateAndroid;
 
   static void DeleteTexture(GLuint id) {
     glDeleteTextures(1, &id);
   }
 
@@ skipping 515 matching lines @@
         data);
   }
   texture_upload_count_++;
   total_texture_upload_time_ += base::TimeTicks::HighResNow() - begin_time;
 
   DCHECK(CHECK_GL());
   return true;
 }
 
 }  // namespace gfx