Enable unused param checking for public includes.

include/core/SkCanvas.h

Index: include/core/SkCanvas.h
diff --git a/include/core/SkCanvas.h b/include/core/SkCanvas.h
index 0cb762afedd1b8e6d44b036d34ab980eb356b656..276b39236fe0cc8bb4caff0ede0e2f89c12aa0ff 100644
--- a/include/core/SkCanvas.h
+++ b/include/core/SkCanvas.h
@@ -1078,7 +1078,7 @@ public:
         subclasses like SkPicture's recording canvas, that can store the data
         and then play it back later (via another call to drawData).
      */
-    virtual void drawData(const void* data, size_t length) {
+    virtual void drawData(const void* /*data*/, size_t /*length*/) {
         // do nothing. Subclasses may do something with the data
     }
 
@@ -1086,10 +1086,10 @@ public:
         Each comment added via addComment is notionally attached to its
         enclosing group. Top-level comments simply belong to no group.
      */
-    virtual void beginCommentGroup(const char* description) {
+    virtual void beginCommentGroup(const char* /*description*/) {
         // do nothing. Subclasses may do something
     }
-    virtual void addComment(const char* kywd, const char* value) {
+    virtual void addComment(const char* /*kywd*/, const char* /*value*/) {
         // do nothing. Subclasses may do something
     }
     virtual void endCommentGroup() {