Make stream captures work on canvases that are not in the DOM.

third_party/WebKit/Source/modules/canvas2d/CanvasRenderingContext2D.h

Index: third_party/WebKit/Source/modules/canvas2d/CanvasRenderingContext2D.h
diff --git a/third_party/WebKit/Source/modules/canvas2d/CanvasRenderingContext2D.h b/third_party/WebKit/Source/modules/canvas2d/CanvasRenderingContext2D.h
index 411e88069cd001b4f10e4cfbb15b6300cb28f10b..623f25edc0d2e1f45d828326297c67b7daf06032 100644
--- a/third_party/WebKit/Source/modules/canvas2d/CanvasRenderingContext2D.h
+++ b/third_party/WebKit/Source/modules/canvas2d/CanvasRenderingContext2D.h
@@ -67,11 +67,9 @@ typedef CSSImageValueOrHTMLImageElementOrHTMLVideoElementOrHTMLCanvasElementOrIm
 class MODULES_EXPORT CanvasRenderingContext2D final
     : public CanvasRenderingContext,
       public BaseRenderingContext2D,
-      public WebThread::TaskObserver,
       public SVGResourceClient {
   DEFINE_WRAPPERTYPEINFO();
   USING_GARBAGE_COLLECTED_MIXIN(CanvasRenderingContext2D);
-  USING_PRE_FINALIZER(CanvasRenderingContext2D, dispose);
 
  public:
   class Factory : public CanvasRenderingContextFactory {
@@ -142,8 +140,7 @@ class MODULES_EXPORT CanvasRenderingContext2D final
   void restoreCanvasMatrixClipStack(PaintCanvas*) const override;
 
   // TaskObserver implementation
-  void didProcessTask() override;
-  void willProcessTask() override {}
+  void didProcessTask() final;
 
   void styleDidChange(const ComputedStyle* oldStyle,
                       const ComputedStyle& newStyle) override;
@@ -208,14 +205,11 @@ class MODULES_EXPORT CanvasRenderingContext2D final
                            const CanvasContextCreationAttributes& attrs,
                            Document&);
 
-  void dispose();
-
   void dispatchContextLostEvent(TimerBase*);
   void dispatchContextRestoredEvent(TimerBase*);
   void tryRestoreContextEvent(TimerBase*);
 
   void pruneLocalFontCache(size_t targetSize);
-  void schedulePruneLocalFontCacheIfNeeded();
 
   void scrollPathIntoViewInternal(const Path&);
 
@@ -257,7 +251,7 @@ class MODULES_EXPORT CanvasRenderingContext2D final
 
   FilterOperations m_filterOperations;
   HashMap<String, Font> m_fontsResolvedUsingCurrentStyle;
-  bool m_pruneLocalFontCacheScheduled;
+  bool m_shouldPruneLocalFontCache;
   ListHashSet<String> m_fontLRUList;
 };