Early terminate WebGL markContextChanged calls when appropriate

third_party/WebKit/Source/platform/graphics/gpu/DrawingBuffer.cpp

Index: third_party/WebKit/Source/platform/graphics/gpu/DrawingBuffer.cpp
diff --git a/third_party/WebKit/Source/platform/graphics/gpu/DrawingBuffer.cpp b/third_party/WebKit/Source/platform/graphics/gpu/DrawingBuffer.cpp
index 4023f3420e751291d9cc97de1e9cabda9e7bc632..49461bdb4efb962adb020860d0f2485ec03eabc1 100644
--- a/third_party/WebKit/Source/platform/graphics/gpu/DrawingBuffer.cpp
+++ b/third_party/WebKit/Source/platform/graphics/gpu/DrawingBuffer.cpp
@@ -164,9 +164,13 @@ DrawingBuffer::~DrawingBuffer() {
   m_contextProvider.reset();
 }
 
-void DrawingBuffer::markContentsChanged() {
-  m_contentsChanged = true;
-  m_contentsChangeCommitted = false;
+bool DrawingBuffer::markContentsChanged() {
+  if (m_contentsChangeCommitted || !m_contentsChanged) {
+    m_contentsChangeCommitted = false;
+    m_contentsChanged = true;
+    return true;
+  }
+  return false;
 }
 
 bool DrawingBuffer::bufferClearNeeded() const {