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, 19 insertions, 0 deletions

diff --git a/src/utils/SkNWayCanvas.cpp b/src/utils/SkNWayCanvas.cpp
index c612c7d7e1..687413d765 100644
--- a/src/utils/SkNWayCanvas.cpp
+++ b/src/utils/SkNWayCanvas.cpp
@@ -4,7 +4,9 @@
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
+
 #include "SkNWayCanvas.h"
+#include "SkCanvasPriv.h"
 
 SkNWayCanvas::SkNWayCanvas(int width, int height) : INHERITED(width, height) {}
 
@@ -45,6 +47,7 @@ public:
         return false;
     }
     SkCanvas* operator->() { return fCanvas; }
+    SkCanvas* get() const { return fCanvas; }
 
 private:
     const SkTDArray<SkCanvas*>& fList;
@@ -72,6 +75,15 @@ SkCanvas::SaveLayerStrategy SkNWayCanvas::getSaveLayerStrategy(const SaveLayerRe
     return kNoLayer_SaveLayerStrategy;
 }
 
+bool SkNWayCanvas::onDoSaveBehind(const SkRect* bounds) {
+    Iter iter(fList);
+    while (iter.next()) {
+        SkCanvasPriv::SaveBehind(iter.get(), bounds);
+    }
+    this->INHERITED::onDoSaveBehind(bounds);
+    return false;
+}
+
 void SkNWayCanvas::willRestore() {
     Iter iter(fList);
     while (iter.next()) {
@@ -135,6 +147,13 @@ void SkNWayCanvas::onDrawPaint(const SkPaint& paint) {
     }
 }
 
+void SkNWayCanvas::onDrawBehind(const SkPaint& paint) {
+    Iter iter(fList);
+    while (iter.next()) {
+        SkCanvasPriv::DrawBehind(iter.get(), paint);
+    }
+}
+
 void SkNWayCanvas::onDrawPoints(PointMode mode, size_t count, const SkPoint pts[],
                                 const SkPaint& paint) {
     Iter iter(fList);