Make OffscreenCanvas WebGL(2) context consider taintedness of image source

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 cd01183f9d03c1a3ee3e03dbfc695c223769cf56..30df6b578f0560fce93bb0da91feb8055bacda8b 100644
--- a/third_party/WebKit/Source/core/html/canvas/CanvasRenderingContext.cpp
+++ b/third_party/WebKit/Source/core/html/canvas/CanvasRenderingContext.cpp
@@ -231,12 +231,8 @@ bool CanvasRenderingContext::WouldTaintOrigin(
       return true;
   }
 
-  DCHECK_EQ(!canvas(),
-            !!destination_security_origin);  // Must have one or the other
-  bool taint_origin = image_source->WouldTaintOrigin(
-      destination_security_origin ? destination_security_origin
-                                  : canvas()->GetSecurityOrigin());
-
+  bool taint_origin =
+      image_source->WouldTaintOrigin(destination_security_origin);

[Justin Novosad, 2017/04/12 14:53:40]

Just checking: I assume OCRC2D was already calling this correctly and with a
non-null destination_security_origin, and we already have tests for that?

[xlai (Olivia), 2017/04/12 19:37:28]

Yes, OCRC2D is already doing this correct. It calls WouldTaintOrigin in two
functions and each has its own security test:
drawImage:
LayoutTests/http/tests/security/offscreencanvas-read-blocked-no-crossorigin.html
createPattern:
LayoutTests/http/tests/security/cross-origin-OffscreenCanvas2D-createPattern.html

   if (has_url) {
     if (taint_origin)
       dirty_ur_ls_.insert(source_url.GetString());