Use dictionaries for context creation attributes. Eliminate custom bindings.

Source/core/html/canvas/CanvasRenderingContext2D.cpp

Index: Source/core/html/canvas/CanvasRenderingContext2D.cpp
diff --git a/Source/core/html/canvas/CanvasRenderingContext2D.cpp b/Source/core/html/canvas/CanvasRenderingContext2D.cpp
index c98b4a4759a096245ce17b716a1df0a8aa002901..92795cecba1e77eaf184ac50d74b1fcb20fb2c6b 100644
--- a/Source/core/html/canvas/CanvasRenderingContext2D.cpp
+++ b/Source/core/html/canvas/CanvasRenderingContext2D.cpp
@@ -90,14 +90,27 @@ static bool contextLostRestoredEventsEnabled()
     return RuntimeEnabledFeatures::experimentalCanvasFeaturesEnabled();
 }
 
-CanvasRenderingContext2D::CanvasRenderingContext2D(HTMLCanvasElement* canvas, const Canvas2DContextAttributes* attrs, Document& document)
+static Canvas2DContextStorage storageFromAttributes(const CanvasContextCreationAttributes& attrs)
+{
+    if (!RuntimeEnabledFeatures::experimentalCanvasFeaturesEnabled())
+        return PersistentStorage;
+
+    // The other valid option is "persistent" -- but since the default
+    // is Persistent, it isn't necessary to test for it explicitly.
+    if (attrs.hasStorage() && attrs.storage() == "discardable") {
+        return DiscardableStorage;
+    }
+    return PersistentStorage;
+}
+
+CanvasRenderingContext2D::CanvasRenderingContext2D(HTMLCanvasElement* canvas, const CanvasContextCreationAttributes& attrs, Document& document)
     : CanvasRenderingContext(canvas)
     , m_usesCSSCompatibilityParseMode(document.inQuirksMode())
     , m_clipAntialiasing(NotAntiAliased)
-    , m_hasAlpha(!attrs || attrs->alpha())
+    , m_hasAlpha(attrs.alpha())
     , m_isContextLost(false)
     , m_contextRestorable(true)
-    , m_storageMode(!attrs ? PersistentStorage : attrs->parsedStorage())
+    , m_storageMode(storageFromAttributes(attrs))
     , m_tryRestoreContextAttemptCount(0)
     , m_dispatchContextLostEventTimer(this, &CanvasRenderingContext2D::dispatchContextLostEvent)
     , m_dispatchContextRestoredEventTimer(this, &CanvasRenderingContext2D::dispatchContextRestoredEvent)
@@ -2227,11 +2240,12 @@ void CanvasRenderingContext2D::setImageSmoothingEnabled(bool enabled)
         c->setImageInterpolationQuality(enabled ? CanvasDefaultInterpolationQuality : InterpolationNone);
 }
 
-PassRefPtrWillBeRawPtr<Canvas2DContextAttributes> CanvasRenderingContext2D::getContextAttributes() const
+void CanvasRenderingContext2D::getContextAttributes(Canvas2DContextAttributes& attrs) const
 {
-    RefPtrWillBeRawPtr<Canvas2DContextAttributes> attributes = Canvas2DContextAttributes::create();
-    attributes->setAlpha(m_hasAlpha);
-    return attributes.release();
+    attrs.setAlpha(m_hasAlpha);
+    if (RuntimeEnabledFeatures::experimentalCanvasFeaturesEnabled()) {
+        attrs.setStorage(m_storageMode == PersistentStorage ? "persistent" : "discardable");
+    }
 }
 
 void CanvasRenderingContext2D::drawFocusIfNeeded(Element* element)