Inflate rect instead of m_dirtyRect in HTMLCanvasElement::didDraw

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 5c8f2329b9f16f6332811ff126ce444d048ada06..52556b3111db5cba61a8c639ea8039108964a793 100644
--- a/third_party/WebKit/Source/core/html/HTMLCanvasElement.cpp
+++ b/third_party/WebKit/Source/core/html/HTMLCanvasElement.cpp
@@ -269,9 +269,13 @@ void HTMLCanvasElement::didDraw(const FloatRect& rect)
     clearCopiedImage();
     if (layoutObject())
         layoutObject()->setMayNeedPaintInvalidation();
-    m_dirtyRect.unite(rect);
-    if (m_context && m_context->is2d() && m_context->shouldAntialias() && page() && page()->deviceScaleFactor() > 1.0f)
-        m_dirtyRect.inflate(1);
+    if (m_context && m_context->is2d() && m_context->shouldAntialias() && page() && page()->deviceScaleFactor() > 1.0f) {
+        FloatRect inflatedRect = rect;
+        inflatedRect.inflate(1);
+        m_dirtyRect.unite(inflatedRect);
+    } else {
+        m_dirtyRect.unite(rect);
+    }
     if (m_context && m_context->is2d() && hasImageBuffer())
         buffer()->didDraw(rect);
 }