Surface Synchronization: Don't force commit on content_source_id

It should never be necessary to force a commit when a content_source_id changes.

Cq-Include-Trybots: luci.chromium.try:android_optional_gpu_tests_rel;master.tryserver.blink:linux_trusty_blink_rel
Change-Id: I58bd6d840feca9df58bd674e2a42cf987bba2ed5
Bug: 847383, 672962
Reviewed-on: https://chromium-review.googlesource.com/1124760Reviewed-by: Saman Sami <samans@chromium.org>
Commit-Queue: Fady Samuel <fsamuel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#572619}

cc/trees/layer_tree_host.cc

@@ -1207,10 +1207,7 @@ void LayerTreeHost::SetRasterColorSpace(
 }
 
 void LayerTreeHost::SetContentSourceId(uint32_t id) {
-  if (content_source_id_ == id)
-    return;
   content_source_id_ = id;
-  SetNeedsCommit();
 }
 
 void LayerTreeHost::SetLocalSurfaceIdFromParent(