gfx: Rename canvas SaveAndUnscale to UnscaleTheDeviceScaleFactor.

This changes the method to only do the unscaling. Callers use a
ScopedCanvas instead. Then they don't need to call Restore()
themselves.

R=pkasting, sky

Review URL: https://codereview.chromium.org/1425163002

Cr-Commit-Position: refs/heads/master@{#357172}

4 files changed, 15 insertions, 21 deletions

diff --git a/ui/gfx/canvas.cc b/ui/gfx/canvas.cc
index 2465cfae..b81f995 100644
--- a/ui/gfx/canvas.cc
+++ b/ui/gfx/canvas.cc
@@ -175,17 +175,16 @@ void Canvas::DrawDashedRect(const Rect& rect, SkColor color) {
            paint);
 }
 
-void Canvas::Save() {
-  canvas_->save();
-}
-
-float Canvas::SaveAndUnscale() {
-  Save();
+float Canvas::UndoDeviceScaleFactor() {
   SkScalar scale_factor = 1.0f / image_scale_;
   canvas_->scale(scale_factor, scale_factor);
   return image_scale_;
 }
 
+void Canvas::Save() {
+  canvas_->save();
+}
+
 void Canvas::SaveLayerAlpha(uint8 alpha) {
   canvas_->saveLayerAlpha(NULL, alpha);
 }
diff --git a/ui/gfx/canvas.h b/ui/gfx/canvas.h
index 8183dfa..fd6e3c7 100644
--- a/ui/gfx/canvas.h
+++ b/ui/gfx/canvas.h
@@ -165,15 +165,15 @@ class GFX_EXPORT Canvas {
   // Draws a dashed rectangle of the specified color.
   void DrawDashedRect(const Rect& rect, SkColor color);
 
+  // Unscales by the image scale factor (aka device scale factor), and returns
+  // that factor.  This is useful when callers want to draw directly in the
+  // native scale.
+  float UndoDeviceScaleFactor();
+
   // Saves a copy of the drawing state onto a stack, operating on this copy
   // until a balanced call to Restore() is made.
   void Save();
 
-  // Saves the drawing state, unscales by the image scale factor, and returns
-  // that factor.  This is useful when callers want to draw directly in the
-  // native scale.
-  float SaveAndUnscale();
-
   // As with Save(), except draws to a layer that is blended with the canvas
   // at the specified alpha once Restore() is called.
   // |layer_bounds| are the bounds of the layer relative to the current
diff --git a/ui/gfx/nine_image_painter.cc b/ui/gfx/nine_image_painter.cc
index 040678d..49be5ee 100644
--- a/ui/gfx/nine_image_painter.cc
+++ b/ui/gfx/nine_image_painter.cc
@@ -88,8 +88,11 @@ void NineImagePainter::Paint(Canvas* canvas,
   if (IsEmpty())
     return;
 
-  // Painting at physical device pixels (undo device scale factor).
-  float scale = canvas->SaveAndUnscale();
+  ScopedCanvas scoped_canvas(canvas);
+
+  // Painting and doing layout at physical device pixels to avoid cracks or
+  // overlap.
+  const float scale = canvas->UndoDeviceScaleFactor();
 
   // Since the drawing from the following Fill() calls assumes the mapped origin
   // is at (0,0), we need to translate the canvas to the mapped origin.
@@ -163,8 +166,6 @@ void NineImagePainter::Paint(Canvas* canvas,
     Fill(canvas, image_reps[8], width_in_pixels - i8w, height_in_pixels - i8h,
          i8w, i8h, paint);
   }
-
-  canvas->Restore();
 }
 
 // static
diff --git a/ui/gfx/scoped_canvas.h b/ui/gfx/scoped_canvas.h
index 2e59a07..7701f7c 100644
--- a/ui/gfx/scoped_canvas.h
+++ b/ui/gfx/scoped_canvas.h
@@ -20,12 +20,6 @@ class ScopedCanvas {
     if (canvas_)
       canvas_->Restore();
   }
-  void SetCanvas(gfx::Canvas* canvas) {
-    if (canvas_)
-      canvas_->Restore();
-    canvas_ = canvas;
-    canvas_->Save();
-  }
 
  private:
   gfx::Canvas* canvas_;