Fix filter primitive bounds computations.

src/effects/SkComposeImageFilter.cpp

Index: src/effects/SkComposeImageFilter.cpp
diff --git a/src/effects/SkComposeImageFilter.cpp b/src/effects/SkComposeImageFilter.cpp
index 1be03a337084e3abfe31d84ffcc21fc6791f7a35..59159551ccafee97ccba7c3f45cfe78ea799f63a 100644
--- a/src/effects/SkComposeImageFilter.cpp
+++ b/src/effects/SkComposeImageFilter.cpp
@@ -35,7 +35,9 @@ bool SkComposeImageFilter::onFilterImage(Proxy* proxy,
 
     SkMatrix outerMatrix(ctx.ctm());
     outerMatrix.postTranslate(SkIntToScalar(-innerOffset.x()), SkIntToScalar(-innerOffset.y()));
-    Context outerContext(outerMatrix, ctx.clipBounds(), ctx.cache(), ctx.sizeConstraint());
+    SkIRect clipBounds = ctx.clipBounds();
+    clipBounds.offset(-innerOffset.x(), -innerOffset.y());
+    Context outerContext(outerMatrix, clipBounds, ctx.cache(), ctx.sizeConstraint());
     if (!this->filterInput(0, proxy, tmp, outerContext, result, &outerOffset, false)) {
         return false;
     }