Expose FillBounds to allow GrPictureUtils::CollectLayers to be layered on top of it

tests/PictureTest.cpp

Index: tests/PictureTest.cpp
diff --git a/tests/PictureTest.cpp b/tests/PictureTest.cpp
index 1dc37e32edd99f60ea8e7b9cf55d4069cd7b9c22..edbfdb3f57d2994c01a82644edcca56eecbfe0d9 100644
--- a/tests/PictureTest.cpp
+++ b/tests/PictureTest.cpp
@@ -1021,11 +1021,12 @@ static void test_gpu_picture_optimization(skiatest::Reporter* reporter,
             REPORTER_ASSERT(reporter, !info0.fIsNested && !info0.fHasNestedLayers);
 
             REPORTER_ASSERT(reporter, NULL == info1.fPicture);
-            REPORTER_ASSERT(reporter, kWidth == info1.fBounds.width() &&
-                                      kHeight == info1.fBounds.height());
+            REPORTER_ASSERT(reporter, kWidth/2.0f == info1.fBounds.width() &&
+                                      kHeight/2.0f == info1.fBounds.height());
             REPORTER_ASSERT(reporter, info1.fLocalMat.isIdentity());
             REPORTER_ASSERT(reporter, info1.fPreMat.isIdentity());
-            REPORTER_ASSERT(reporter, 0 == info1.fBounds.fLeft && 0 == info1.fBounds.fTop);
+            REPORTER_ASSERT(reporter, kWidth / 2.0f == info1.fBounds.fLeft &&
+                                      kHeight / 2.0f == info1.fBounds.fTop);
             REPORTER_ASSERT(reporter, NULL == info1.fPaint);
             REPORTER_ASSERT(reporter, !info1.fIsNested &&
                                       info1.fHasNestedLayers); // has a nested SL