Improving canvas 2D performance by switching graphics rendering pipeline.

third_party/WebKit/Source/core/html/HTMLCanvasElement.cpp

Index: third_party/WebKit/Source/core/html/HTMLCanvasElement.cpp
diff --git a/third_party/WebKit/Source/core/html/HTMLCanvasElement.cpp b/third_party/WebKit/Source/core/html/HTMLCanvasElement.cpp
index ca1f5ac6b3c46766c330ea23d7032a3c969c193e..17e1eed62e0148d0232fe6c275709155072abd12 100644
--- a/third_party/WebKit/Source/core/html/HTMLCanvasElement.cpp
+++ b/third_party/WebKit/Source/core/html/HTMLCanvasElement.cpp
@@ -148,6 +148,7 @@ inline HTMLCanvasElement::HTMLCanvasElement(Document& document)
     , m_originClean(true)
     , m_didFailToCreateImageBuffer(false)
     , m_imageBufferIsClear(false)
+    , m_numFramesSinceLastRenderingModeSwitch(0)
 {
     CanvasMetrics::countCanvasContextUsage(CanvasMetrics::CanvasCreated);
 }
@@ -316,6 +317,25 @@ void HTMLCanvasElement::didFinalizeFrame()
         ro->invalidatePaintRectangle(mappedDirtyRect);
     }
     m_dirtyRect = FloatRect();
+
+    m_numFramesSinceLastRenderingModeSwitch++;
+    if (m_context->is2d() && buffer()->isAccelerated()
+        && m_numFramesSinceLastRenderingModeSwitch >= ExpensiveCanvasHeuristicParameters::MinFramesBeforeSwitch) {
+        if (RuntimeEnabledFeatures::enableCanvas2dDynamicRenderingModeSwitchingEnabled()) {

[Stephen White, 2016/07/19 15:47:41]

Nit: perhaps this check should be outside of all of this code (ie., above line
321 above). Would that make sense?

[sebastienlc, 2016/07/19 18:59:24]

Done.

+            if (!m_context->isAccelerationOptimalForCanvasContent()) {
+                // The switch must be done asynchronously in order to avoid switching during the paint invalidation step.
+                Platform::current()->currentThread()->getWebTaskRunner()->postTask(
+                    BLINK_FROM_HERE,
+                    WTF::bind([](WeakPtr<ImageBuffer> buffer) {

[Stephen White, 2016/07/19 15:47:41]

Do you still need WTF::bind() here, or could you just use the lambda directly?
The type conversion *should* just work without the bind(), although I'm
half-speculating here. Maybe give it a try?

[sebastienlc, 2016/07/19 18:59:24]

I tried but the type conversion doesn't seem to work.

+                        if (buffer) {
+                            buffer->disableAcceleration();
+                        }
+                    },
+                    m_imageBuffer->m_weakPtrFactory.createWeakPtr()));
+                m_numFramesSinceLastRenderingModeSwitch = 0;
+            }
+        }
+    }
 }
 
 void HTMLCanvasElement::didDisableAcceleration()