Implement canComputeFastBounds() for image filters.

src/core/SkPaint.cpp

Index: src/core/SkPaint.cpp
diff --git a/src/core/SkPaint.cpp b/src/core/SkPaint.cpp
index f64ab1d844784a02b1028ad5cdf16dd6fc0080f1..4ab8927114491bc2650595301a5b45f9efef0eed 100644
--- a/src/core/SkPaint.cpp
+++ b/src/core/SkPaint.cpp
@@ -2063,6 +2063,16 @@ bool SkPaint::getFillPath(const SkPath& src, SkPath* dst, const SkRect* cullRect
     return !rec.isHairlineStyle();
 }
 
+bool SkPaint::canComputeFastBounds() const {
+    if (this->getLooper()) {
+        return this->getLooper()->canComputeFastBounds(*this);
+    }
+    if (this->getImageFilter() && !this->getImageFilter()->canComputeFastBounds()) {
+        return false;
+    }
+    return !this->getRasterizer();
+}
+
 const SkRect& SkPaint::doComputeFastBounds(const SkRect& origSrc,
                                            SkRect* storage,
                                            Style style) const {