Re-enable imageresizetiled, but skip it in tilegrid and rtree.

This change makes kSkipTiled_Flag also skip --tileGrid and --rtree.
All GMs which were passing kSkipTiled_Flag before were also passing
kSkipPicture_Flag, which also skips tilegrid and rtree, so this should
have no effect on them, but provides a smaller hammer for GMs which
still want to test picture playback, but not tiling.

The exception is magnifier, which was passing only kSkipTiled_Flag,
but magnifier is an odd beast and not web-exposed, so I'm not worried
about reducing its coverage slightly.

R=scroggo@google.com
BUG=skia:

Review URL: https://codereview.chromium.org/165723009

git-svn-id: http://skia.googlecode.com/svn/trunk@13514 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/gm/imageresizetiled.cpp b/gm/imageresizetiled.cpp
index a54c811..ba154d1 100644
--- a/gm/imageresizetiled.cpp
+++ b/gm/imageresizetiled.cpp
@@ -30,6 +30,10 @@
         return make_isize(WIDTH, HEIGHT);
     }
 
+    virtual uint32_t onGetFlags() const SK_OVERRIDE {
+        return kSkipTiled_Flag;
+    }
+
     virtual void onDraw(SkCanvas* canvas) SK_OVERRIDE {
         SkPaint paint;
         SkAutoTUnref<SkImageFilter> imageFilter(