Make WebKitCSSMatrix an alias of DOMMatrix

third_party/WebKit/Source/core/css/WebKitCSSMatrix.idl

Index: third_party/WebKit/Source/core/css/WebKitCSSMatrix.idl
diff --git a/third_party/WebKit/Source/core/css/WebKitCSSMatrix.idl b/third_party/WebKit/Source/core/css/WebKitCSSMatrix.idl
index 361076611fcead652685a768a8dd32b93cd04d02..509c336beea4e86685eebcfa745957f077378eea 100644
--- a/third_party/WebKit/Source/core/css/WebKitCSSMatrix.idl
+++ b/third_party/WebKit/Source/core/css/WebKitCSSMatrix.idl
@@ -59,7 +59,7 @@
     [RaisesException] void setMatrixValue([Default=Undefined] optional DOMString string);
 
     // Multiply this matrix by secondMatrix, on the right (result = this * secondMatrix)
-    [LegacyInterfaceTypeChecking] WebKitCSSMatrix multiply([Default=Undefined] optional WebKitCSSMatrix secondMatrix);
+    [LegacyInterfaceTypeChecking, RaisesException] WebKitCSSMatrix multiply([Default=Undefined] optional WebKitCSSMatrix secondMatrix);
 
     // Return the inverse of this matrix. Throw an exception if the matrix is not invertible
     [RaisesException] WebKitCSSMatrix inverse();