Add some plumbing for the color management of canvases

third_party/WebKit/public/platform/WebExternalTextureMailbox.h

Index: third_party/WebKit/public/platform/WebExternalTextureMailbox.h
diff --git a/third_party/WebKit/public/platform/WebExternalTextureMailbox.h b/third_party/WebKit/public/platform/WebExternalTextureMailbox.h
index 0bb41cfd87bcb188c2c6d0c8caafad4a93ae54dc..efb251c446dbeb33782e68189c2cdd867a78af52 100644
--- a/third_party/WebKit/public/platform/WebExternalTextureMailbox.h
+++ b/third_party/WebKit/public/platform/WebExternalTextureMailbox.h
@@ -33,6 +33,8 @@
 
 #include "WebSize.h"
 
+class SkColorSpace;
+
 namespace blink {
 
 struct WebExternalTextureMailbox {
@@ -44,11 +46,21 @@ struct WebExternalTextureMailbox {
     unsigned textureTarget = 0;
     WebSize textureSize;
 
+    // Note: This should really not be a pointer, or be an sk_sp, but
+    // SkColorSpace is non-copyable and passing an sk_sp over
+    // the blink API boundary causes heap corruption, so we are using
+    // a raw pointer. This is safe because WebExternalTextureMailbox
+    // objects are ephemeral and never outlive the SkColorSpace object
+    // in the current implementation.
+    const SkColorSpace* colorSpace;
+
     WebExternalTextureMailbox()
     {
         memset(name, 0, sizeof(name));
         memset(syncToken, 0, sizeof(syncToken));
     }
+
+    ~WebExternalTextureMailbox() { }
 };
 
 inline bool nameEquals(const WebExternalTextureMailbox& a, const WebExternalTextureMailbox& b)