Add private save-behind and draw-behind methods to canvas.HEADp9.0

The draw-behind  is a variant of drawPaint but is automatically clipped
to the bounds of the most recent saveBehind buffer (axis-aligned bounds).

No public exposure outside of the Android framework.

Impl is pretty simple (its a variant of drawPaint)
- find the most recent saveBehind device bounds
- if there is none, draw nothing, else
  - temporarily intersect the device's clip with that bounds
  - drawPaint
  - restore the clip

This patches did not apply cleanly and have been updated to compile
with a previous version of Skia. It was cherry-picked from the
following 3 Skia commits:
148b7fd3ad9c29dec0052de624c26ff291ef8f0a
d567408362bf7847d6000f6786f9a7b2c9d0b88b
9adc82c73df0ef25b708cae8aa48ef9c39ed4c67

Bug: 129117085
Test: None
Change-Id: I291f57885de6e95f749bf5cdb70ac16a5781ffb1

1 files changed, 8 insertions, 0 deletions

diff --git a/src/core/SkCanvasPriv.h b/src/core/SkCanvasPriv.h
index 12d9fce027..e1eb02fd45 100644
--- a/src/core/SkCanvasPriv.h
+++ b/src/core/SkCanvasPriv.h
@@ -33,6 +33,14 @@ public:
     // return the byte-size of the lattice, even if the buffer is null
     // storage must be 4-byte aligned
     static size_t WriteLattice(void* storage, const SkCanvas::Lattice&);
+
+    static int SaveBehind(SkCanvas* canvas, const SkRect* subset) {
+        return canvas->only_axis_aligned_saveBehind(subset);
+    }
+
+    static void DrawBehind(SkCanvas* canvas, const SkPaint& paint) {
+        canvas->drawClippedToSaveBehind(paint);
+    }
 };
 
 #endif