Fix filter primitive bounds computations.

src/core/SkRecordDraw.cpp

Index: src/core/SkRecordDraw.cpp
diff --git a/src/core/SkRecordDraw.cpp b/src/core/SkRecordDraw.cpp
index 4847273f52a826f4eb2510abb75b4e7860cc82d2..90b85d1e969e63277b0eef6679576049c0e15d11 100644
--- a/src/core/SkRecordDraw.cpp
+++ b/src/core/SkRecordDraw.cpp
@@ -221,6 +221,7 @@ private:
         int controlOps;        // Number of control ops in this Save block, including the Save.
         Bounds bounds;         // Bounds of everything in the block.
         const SkPaint* paint;  // Unowned.  If set, adjusts the bounds of all ops in this block.
+        SkMatrix ctm;
     };
 
     // Only Restore, SetMatrix, and Concat change the CTM.
@@ -301,6 +302,7 @@ private:
         sb.bounds =
             PaintMayAffectTransparentBlack(paint) ? fCurrentClipBounds : Bounds::MakeEmpty();
         sb.paint = paint;
+        sb.ctm = this->fCTM;
 
         fSaveStack.push(sb);
         this->pushControl();
@@ -563,9 +565,15 @@ private:
 
     bool adjustForSaveLayerPaints(SkRect* rect, int savesToIgnore = 0) const {
         for (int i = fSaveStack.count() - 1 - savesToIgnore; i >= 0; i--) {
+            SkMatrix inverse;
+            if (!fSaveStack[i].ctm.invert(&inverse)) {
+                return false;
+            }
+            inverse.mapRect(rect);
             if (!AdjustForPaint(fSaveStack[i].paint, rect)) {
                 return false;
             }
+            fSaveStack[i].ctm.mapRect(rect);

[mtklein, 2015/12/09 16:59:41]

Is it important that we do rect = (M (M^-1 rect)) here?

I'd just have expected to stash away the original rect and restore it by a
simple copy instead of re-mapping.

[mtklein, 2015/12/09 17:00:53]

(Or put (M^-1 rect) into another SkRect instead of doing it in place in rect?)

[Stephen White, 2015/12/09 17:02:57]

The problem is that we don't know the rect at saveLayer time: we're trying to
map some primitive that we're drawing [1..N] saveLayers 
deep.

That said, at a minimum I should probably stash the matrix inverse on 
the save stack as well, to avoid inverting it each time.

[mtklein, 2015/12/09 17:06:04]

So, (*rect at line 577) != (*rect at line 571)?

[Stephen White, 2015/12/09 17:10:52]

Yeah. It may have been munged by AdjustForPaint(). I'm essentially 
attempting to ensure that that munging is done relative to the 
layer's origin, which unfortunately we don't have access to here.

[mtklein, 2015/12/09 17:15:25]

Oh, of course.  That's the whole point of this method.  Duh.

I'm ok to wait until we see the inverts matter on a profile before we stash the
inverse.

         }
         return true;
     }