add asAShadowBlur for android to drawlooper

include/core/SkDrawLooper.h

Index: include/core/SkDrawLooper.h
diff --git a/include/core/SkDrawLooper.h b/include/core/SkDrawLooper.h
index cc42952d07acc289ce21ee2cbd75de5a0a74c4e9..0e7643c40d450786b7763cfa0bd1ba144b3bb052 100644
--- a/include/core/SkDrawLooper.h
+++ b/include/core/SkDrawLooper.h
@@ -11,6 +11,8 @@
 #define SkDrawLooper_DEFINED
 
 #include "SkFlattenable.h"
+#include "SkPoint.h"
+#include "SkColor.h"
 
 class SkCanvas;
 class SkPaint;
@@ -88,6 +90,22 @@ public:
     virtual void computeFastBounds(const SkPaint& paint,
                                    const SkRect& src, SkRect* dst) const;
 
+    struct BlurShadowRec {
+        SkScalar    fRadius;

[djsollen, 2014/04/28 13:55:40]

As we discussed offline, I think this should return sigma so we can let the
caller do the conversion if they want to.

+        SkVector    fOffset;
+        SkColor     fColor;
+    };
+    /**
+     *  If this looper can be interpreted as having two layers, such that
+     *      1. The first layer (bottom most) just has a color, blur, and translate
+     *      2. The second layer has no modifications to either paint or canvas
+     *      3. No other layers.
+     *  then return true, and if not null, fill out the BlurShadowRec).
+     *
+     *  If any of the above are not met, return false and ignore the BlurShadowRec parameter.
+     */
+    virtual bool asABlurShadow(BlurShadowRec*) const;

[scroggo, 2014/04/28 13:28:06]

Does this need to be on the base class? It seems very specific to one subclass.

[djsollen, 2014/04/28 13:55:40]

It does need to be on the base class since it allows you to inspect any
DrawLooper and see if it is just implementing a blur.  The subclasses that do
not will just return false.

+
     SK_TO_STRING_PUREVIRT()
     SK_DEFINE_FLATTENABLE_TYPE(SkDrawLooper)