Move SkRecordComputeLayers and CollectLayers into SkRecordDraw.cpp

Rather then exposing parts of FillBounds (as in Expose FillBounds to allow GrPictureUtils::CollectLayers to be layered on top of it - https://codereview.chromium.org/698643002/), this CL moves CollectLayers into SkRecordDraw.cpp to accomplish the layering.

Review URL: https://codereview.chromium.org/716913003
diff --git a/tests/PictureTest.cpp b/tests/PictureTest.cpp
index 42bd258..3cb145e 100644
--- a/tests/PictureTest.cpp
+++ b/tests/PictureTest.cpp
@@ -1018,11 +1018,12 @@
             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/2.0 == info1.fBounds.width() &&
+                                      kHeight/2.0 == 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/2.0 == info1.fBounds.fLeft && 
+                                      kHeight/2.0 == info1.fBounds.fTop);
             REPORTER_ASSERT(reporter, NULL == info1.fPaint);
             REPORTER_ASSERT(reporter, !info1.fIsNested &&
                                       info1.fHasNestedLayers); // has a nested SL