cc: Make --jank-instead-of-checkerboard jank more often

cc/thread_proxy.cc

 // Copyright 2011 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 "config.h"
 
 #include "cc/thread_proxy.h"
 
 #include "base/debug/trace_event.h"
 #include "cc/delay_based_time_source.h"
 #include "cc/draw_quad.h"
 #include "cc/frame_rate_controller.h"
 #include "cc/graphics_context.h"
 #include "cc/input_handler.h"
 #include "cc/layer_tree_host.h"
 #include "cc/scheduler.h"
 #include "cc/scoped_thread_proxy.h"
+#include "cc/settings.h"
 #include "cc/thread_task.h"
 #include <public/WebSharedGraphicsContext3D.h>
 #include <wtf/CurrentTime.h>
 
 using WebKit::WebSharedGraphicsContext3D;
 
 namespace {
 
 // Measured in seconds.
 const double contextRecreationTickRate = 0.03;
@@ skipping 669 matching lines @@
     // This method is called on a forced draw, regardless of whether we are able to produce a frame,
     // as the calling site on main thread is blocked until its request completes, and we signal
     // completion here. If canDraw() is false, we will indicate success=false to the caller, but we
     // must still signal completion to avoid deadlock.
 
     // We guard prepareToDraw() with canDraw() because it always returns a valid frame, so can only
     // be used when such a frame is possible. Since drawLayers() depends on the result of
     // prepareToDraw(), it is guarded on canDraw() as well.
 
     LayerTreeHostImpl::FrameData frame;
-    bool drawFrame = m_layerTreeHostImpl->canDraw() && (m_layerTreeHostImpl->prepareToDraw(frame) || forcedDraw);
+    bool drawFrame = false;
+    if (m_layerTreeHostImpl->canDraw()) {
+        drawFrame = m_layerTreeHostImpl->prepareToDraw(frame);
+
+        if (forcedDraw && !Settings::jankInsteadOfCheckerboard())

[danakj, 2012/10/24 20:23:39]

Is this going to break readbacks or whatever else uses forced draws?

Shouldn't we just prevent the forcedDraw from being scheduled?

[enne (OOO), 2012/10/24 20:27:35]

Done.

+            drawFrame = true;
+    }
     if (drawFrame) {
         m_layerTreeHostImpl->drawLayers(frame);
         result.didDraw = true;
     }
     m_layerTreeHostImpl->didDrawAllLayers(frame);
 
     // Check for a pending compositeAndReadback.
     if (m_readbackRequestOnImplThread) {
         m_readbackRequestOnImplThread->success = false;
         if (drawFrame) {
@@ skipping 230 matching lines @@
 ThreadProxy::BeginFrameAndCommitState::BeginFrameAndCommitState()
     : monotonicFrameBeginTime(0)
 {
 }
 
 ThreadProxy::BeginFrameAndCommitState::~BeginFrameAndCommitState()
 {
 }
 
 }  // namespace cc