cc: Move FallbackFence implementation from GLRenderer to ResourceProvider.

cc/resources/resource_provider.cc

Index: cc/resources/resource_provider.cc
diff --git a/cc/resources/resource_provider.cc b/cc/resources/resource_provider.cc
index b638cb749126649edbb6fe13e4626d946efb3bbf..3a59c0b97cf7b2f12d66aa3f891d4321b39d587d 100644
--- a/cc/resources/resource_provider.cc
+++ b/cc/resources/resource_provider.cc
@@ -1130,6 +1130,35 @@ SkSurface* ResourceProvider::ScopedWriteLockGr::GetSkSurface(
   return resource_->sk_surface.get();
 }
 
+ResourceProvider::SynchronousFence::SynchronousFence(
+    gpu::gles2::GLES2Interface* gl)
+    : gl_(gl), has_synchronized_(true) {
+}
+
+ResourceProvider::SynchronousFence::~SynchronousFence() {
+}
+
+void ResourceProvider::SynchronousFence::Set() {
+  has_synchronized_ = false;
+}
+
+bool ResourceProvider::SynchronousFence::HasPassed() {
+  if (!has_synchronized_) {
+    has_synchronized_ = true;
+    Synchronize();
+  }
+  return true;
+}
+
+void ResourceProvider::SynchronousFence::Wait() {
+  HasPassed();
+}
+
+void ResourceProvider::SynchronousFence::Synchronize() {
+  TRACE_EVENT0("cc", "ResourceProvider::SynchronousFence::Synchronize");
+  gl_->Finish();
+}
+
 ResourceProvider::ResourceProvider(
     OutputSurface* output_surface,
     SharedBitmapManager* shared_bitmap_manager,
@@ -2023,11 +2052,12 @@ void ResourceProvider::CopyResource(ResourceId source_id, ResourceId dest_id) {
     gl->BindTexture(source_resource->target, source_resource->gl_id);
     BindImageForSampling(source_resource);
   }
-  DCHECK(use_sync_query_) << "CHROMIUM_sync_query extension missing";
-  if (!source_resource->gl_read_lock_query_id)
-    gl->GenQueriesEXT(1, &source_resource->gl_read_lock_query_id);
-  gl->BeginQueryEXT(GL_COMMANDS_COMPLETED_CHROMIUM,
-                    source_resource->gl_read_lock_query_id);
+  if (use_sync_query_) {
+    if (!source_resource->gl_read_lock_query_id)
+      gl->GenQueriesEXT(1, &source_resource->gl_read_lock_query_id);
+    gl->BeginQueryEXT(GL_COMMANDS_COMPLETED_CHROMIUM,
+                      source_resource->gl_read_lock_query_id);
+  }
   DCHECK(!dest_resource->image_id);
   dest_resource->allocated = true;
   gl->CopyTextureCHROMIUM(dest_resource->target,
@@ -2036,11 +2066,22 @@ void ResourceProvider::CopyResource(ResourceId source_id, ResourceId dest_id) {
                           0,
                           GLInternalFormat(dest_resource->format),
                           GLDataType(dest_resource->format));
-  // End query and create a read lock fence that will prevent access to
-  // source resource until CopyTextureCHROMIUM command has completed.
-  gl->EndQueryEXT(GL_COMMANDS_COMPLETED_CHROMIUM);
-  source_resource->read_lock_fence = make_scoped_refptr(
-      new QueryFence(gl, source_resource->gl_read_lock_query_id));
+  if (source_resource->gl_read_lock_query_id) {
+    // End query and create a read lock fence that will prevent access to
+    // source resource until CopyTextureCHROMIUM command has completed.
+    gl->EndQueryEXT(GL_COMMANDS_COMPLETED_CHROMIUM);
+    source_resource->read_lock_fence = make_scoped_refptr(
+        new QueryFence(gl, source_resource->gl_read_lock_query_id));
+  } else {
+    // Create a SynchronousFence when CHROMIUM_sync_query extension is missing.
+    // Try to use one synchronous fence for as many CopyResource operations as
+    // possible as that reduce the number of times we have to synchronize with
+    // the GL.
+    if (!synchronous_fence_.get() || synchronous_fence_->has_synchronized())
+      synchronous_fence_ = make_scoped_refptr(new SynchronousFence(gl));
+    source_resource->read_lock_fence = synchronous_fence_;
+    source_resource->read_lock_fence->Set();
+  }
 }
 
 void ResourceProvider::WaitSyncPointIfNeeded(ResourceId id) {