Implement wouldTaintOrigin and expose createPattern for OCRC2D on main thread

third_party/WebKit/Source/core/html/canvas/CanvasRenderingContext.cpp

Index: third_party/WebKit/Source/core/html/canvas/CanvasRenderingContext.cpp
diff --git a/third_party/WebKit/Source/core/html/canvas/CanvasRenderingContext.cpp b/third_party/WebKit/Source/core/html/canvas/CanvasRenderingContext.cpp
index 17c1e8141a4f7ca44c039811abf997ab3a304a68..e20ca480ba77bcfaefd668c2aa91bdef1d27b604 100644
--- a/third_party/WebKit/Source/core/html/canvas/CanvasRenderingContext.cpp
+++ b/third_party/WebKit/Source/core/html/canvas/CanvasRenderingContext.cpp
@@ -60,7 +60,7 @@ CanvasRenderingContext::ContextType CanvasRenderingContext::resolveContextTypeAl
     return type;
 }
 
-bool CanvasRenderingContext::wouldTaintOrigin(CanvasImageSource* imageSource)
+bool CanvasRenderingContext::wouldTaintOrigin(CanvasImageSource* imageSource, SecurityOrigin* destinationSecurityOrigin)
 {
     const KURL& sourceURL = imageSource->sourceURL();
     bool hasURL = (sourceURL.isValid() && !sourceURL.isAboutBlankURL());
@@ -72,7 +72,14 @@ bool CanvasRenderingContext::wouldTaintOrigin(CanvasImageSource* imageSource)
             return true;
     }
 
-    bool taintOrigin = imageSource->wouldTaintOrigin(canvas()->getSecurityOrigin());
+    bool taintOrigin;
+    if (!!canvas()) {

[Justin Novosad, 2016/05/05 14:56:16]

I think this bit of code could be made simpler:

ASSERT(!canvas() == !!destinationSecurityOrigin); // Must have one or the other
bool taintOrigin = imageSource->wouldTaintOrigin(destinationSecurityOrigin ?
destinationSecurityOrigin : canvas()->getSecurityOrigin());

+        taintOrigin = imageSource->wouldTaintOrigin(canvas()->getSecurityOrigin());
+    } else {
+        // The function must be called from OffscreenCanvas context then.
+        ASSERT(!!getOffscreenCanvas());
+        taintOrigin = imageSource->wouldTaintOrigin(destinationSecurityOrigin);
+    }
 
     if (hasURL) {
         if (taintOrigin)