2D Canvas: Refactor code re-attempting to allocate an imageBuffer.

Source/core/html/HTMLCanvasElement.cpp

Index: Source/core/html/HTMLCanvasElement.cpp
diff --git a/Source/core/html/HTMLCanvasElement.cpp b/Source/core/html/HTMLCanvasElement.cpp
index c7cca4d73eabc4a4f92fac2aa4b0d86ec78bea16..44c70e50b3bb62d1ac3ff0d7f118cca2b0bbc244 100644
--- a/Source/core/html/HTMLCanvasElement.cpp
+++ b/Source/core/html/HTMLCanvasElement.cpp
@@ -73,7 +73,6 @@ HTMLCanvasElement::HTMLCanvasElement(const QualifiedName& tagName, Document& doc
     , m_ignoreReset(false)
     , m_deviceScaleFactor(1)
     , m_originClean(true)
-    , m_hasCreatedImageBuffer(false)
     , m_didClearImageBuffer(false)
     , m_accelerationDisabled(false)
     , m_externallyAllocatedMemory(0)
@@ -238,7 +237,7 @@ void HTMLCanvasElement::reset()
         return;
 
     bool ok;
-    bool hadImageBuffer = hasCreatedImageBuffer();
+    bool hadImageBuffer = m_imageBuffer.get();
 
     int w = getAttribute(widthAttr).toInt(&ok);
     if (!ok || w < 0)
@@ -265,7 +264,7 @@ void HTMLCanvasElement::reset()
 
     // If the size of an existing buffer matches, we can just clear it instead of reallocating.
     // This optimization is only done for 2D canvases for now.
-    if (m_hasCreatedImageBuffer && oldSize == newSize && m_deviceScaleFactor == newDeviceScaleFactor && m_context && m_context->is2d()) {
+    if (m_imageBuffer && oldSize == newSize && m_deviceScaleFactor == newDeviceScaleFactor && m_context && m_context->is2d()) {
         if (!m_didClearImageBuffer)
             clearImageBuffer();
         return;
@@ -323,15 +322,13 @@ void HTMLCanvasElement::paint(GraphicsContext* context, const LayoutRect& r, boo
         m_context->paintRenderingResultsToCanvas();
     }
 
-    if (hasCreatedImageBuffer()) {
-        ImageBuffer* imageBuffer = buffer();
-        if (imageBuffer) {
-            CompositeOperator compositeOperator = !m_context || m_context->hasAlpha() ? CompositeSourceOver : CompositeCopy;
-            if (m_presentedImage)
-                context->drawImage(m_presentedImage.get(), pixelSnappedIntRect(r), compositeOperator, DoNotRespectImageOrientation, useLowQualityScale);
-            else
-                context->drawImageBuffer(imageBuffer, pixelSnappedIntRect(r), compositeOperator, BlendModeNormal, useLowQualityScale);
-        }
+    ImageBuffer* imageBuffer = buffer();
+    if (imageBuffer) {
+        CompositeOperator compositeOperator = !m_context || m_context->hasAlpha() ? CompositeSourceOver : CompositeCopy;
+        if (m_presentedImage)
+            context->drawImage(m_presentedImage.get(), pixelSnappedIntRect(r), compositeOperator, DoNotRespectImageOrientation, useLowQualityScale);
+        else
+            context->drawImageBuffer(imageBuffer, pixelSnappedIntRect(r), compositeOperator, BlendModeNormal, useLowQualityScale);
     }
 
     if (is3D())
@@ -359,7 +356,6 @@ void HTMLCanvasElement::clearPresentationCopy()
 void HTMLCanvasElement::setSurfaceSize(const IntSize& size)
 {
     m_size = size;
-    m_hasCreatedImageBuffer = false;
     m_contextStateSaver.clear();
     m_imageBuffer.clear();
     setExternallyAllocatedMemory(0);
@@ -478,7 +474,6 @@ void HTMLCanvasElement::createImageBuffer()
 {
     ASSERT(!m_imageBuffer);
 
-    m_hasCreatedImageBuffer = true;
     m_didClearImageBuffer = true;
 
     FloatSize logicalSize = size();
@@ -533,7 +528,7 @@ GraphicsContext* HTMLCanvasElement::drawingContext() const
 
 GraphicsContext* HTMLCanvasElement::existingDrawingContext() const
 {
-    if (!m_hasCreatedImageBuffer)
+    if (!m_imageBuffer)
         return 0;
 
     return drawingContext();
@@ -541,7 +536,7 @@ GraphicsContext* HTMLCanvasElement::existingDrawingContext() const
 
 ImageBuffer* HTMLCanvasElement::buffer() const
 {
-    if (!m_hasCreatedImageBuffer)
+    if (!m_imageBuffer)
         const_cast<HTMLCanvasElement*>(this)->createImageBuffer();
     return m_imageBuffer.get();
 }
@@ -558,7 +553,7 @@ Image* HTMLCanvasElement::copiedImage() const
 
 void HTMLCanvasElement::clearImageBuffer()
 {
-    ASSERT(m_hasCreatedImageBuffer);
+    ASSERT(m_imageBuffer);
     ASSERT(!m_didClearImageBuffer);
     ASSERT(m_context);
 
@@ -579,7 +574,7 @@ void HTMLCanvasElement::clearCopiedImage()
 
 AffineTransform HTMLCanvasElement::baseTransform() const
 {
-    ASSERT(m_hasCreatedImageBuffer);
+    ASSERT(m_imageBuffer);
     FloatSize unscaledSize = size();
     FloatSize deviceSize = convertLogicalToDevice(unscaledSize);
     IntSize size(deviceSize.width(), deviceSize.height());