Remove support for -webkit-canvas and Document.getCSSCanvasContext.

third_party/WebKit/Source/core/frame/UseCounter.cpp

Index: third_party/WebKit/Source/core/frame/UseCounter.cpp
diff --git a/third_party/WebKit/Source/core/frame/UseCounter.cpp b/third_party/WebKit/Source/core/frame/UseCounter.cpp
index 3a84f0065ba222f4a34fc20cc15dcfc81058979d..4bbd1dc49e192906d8fbbf2098affb7f2fc2fd0d 100644
--- a/third_party/WebKit/Source/core/frame/UseCounter.cpp
+++ b/third_party/WebKit/Source/core/frame/UseCounter.cpp
@@ -899,7 +899,7 @@ String UseCounter::deprecationMessage(Feature feature)
         return "requestMediaKeySystemAccess() is deprecated on insecure origins in the specification. Support will be removed in the future. You should consider switching your application to a secure origin, such as HTTPS. See https://goo.gl/rStTGz for more details.";
 
     case DocumentGetCSSCanvasContext:

[pdr., 2015/10/23 18:23:55]

Lets just remove DocumentGetCSSCanvasContext entirely from UseCounter.h and
remove this too.

[chrishtr, 2015/10/23 19:47:06]

Done.

-        return "The -webkit-canvas CSS feature is deprecated. Please use a positioned <canvas> element instead.";
+        ASSERT_NOT_REACHED();
 
     case ElementCreateShadowRootMultiple:
         return "Calling Element.createShadowRoot() for an element which already hosts a shadow root is deprecated. See https://www.chromestatus.com/features/4668884095336448 for more details.";