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}

ash/frame/default_header_painter.cc

@@ -18,6 +18,7 @@
 #include "ui/gfx/font_list.h"
 #include "ui/gfx/geometry/rect.h"
 #include "ui/gfx/image/image.h"
+#include "ui/gfx/scoped_canvas.h"
 #include "ui/gfx/skia_util.h"
 #include "ui/views/view.h"
 #include "ui/views/widget/native_widget_aura.h"
@@ -262,13 +263,13 @@ void DefaultHeaderPainter::PaintTitleBar(gfx::Canvas* canvas) {
 }
 
 void DefaultHeaderPainter::PaintHeaderContentSeparator(gfx::Canvas* canvas) {
-  const float scale = canvas->SaveAndUnscale();
+  gfx::ScopedCanvas scoped_canvas(canvas);
+  const float scale = canvas->UndoDeviceScaleFactor();
   gfx::RectF rect(0, painted_height_ * scale - 1, view_->width() * scale, 1);
   SkPaint paint;
   paint.setColor((mode_ == MODE_ACTIVE) ?
       kHeaderContentSeparatorColor : kHeaderContentSeparatorInactiveColor);
   canvas->sk_canvas()->drawRect(gfx::RectFToSkRect(rect), paint);
-  canvas->Restore();
 }
 
 void DefaultHeaderPainter::LayoutLeftHeaderView() {

chrome/browser/ui/views/bookmarks/bookmark_bar_view.cc

@@ -83,6 +83,7 @@
 #include "ui/gfx/canvas.h"
 #include "ui/gfx/favicon_size.h"
 #include "ui/gfx/paint_vector_icon.h"
+#include "ui/gfx/scoped_canvas.h"
 #include "ui/gfx/text_constants.h"
 #include "ui/gfx/text_elider.h"
 #include "ui/gfx/vector_icons_public.h"
@@ -478,10 +479,11 @@ class BookmarkBarView::ButtonSeparatorView : public views::View {
 
   void OnPaint(gfx::Canvas* canvas) override {
     if (ui::MaterialDesignController::IsModeMaterial()) {
+      gfx::ScopedCanvas scoped_canvas(canvas);
       // 1px wide at all scale factors. If there is an uneven amount of padding
       // left over, place the extra pixel on the outside, i.e. away from the
       // "Other bookmarks" folder.
-      const float scale = canvas->SaveAndUnscale();
+      const float scale = canvas->UndoDeviceScaleFactor();
       const gfx::RectF scaled_bounds =
           gfx::ScaleRect(gfx::RectF(bounds()), scale);
 
@@ -497,7 +499,6 @@ class BookmarkBarView::ButtonSeparatorView : public views::View {
           SkColorSetA(GetThemeProvider()->GetColor(
                           ThemeProperties::COLOR_TOOLBAR_BUTTON_ICON),
                       0x4D));
-      canvas->Restore();
     } else {
       PaintVerticalDivider(
           canvas, kSeparatorStartX, height(), 1, kEdgeDividerColor,

chrome/browser/ui/views/frame/browser_view.cc

@@ -134,6 +134,7 @@
 #include "ui/gfx/canvas.h"
 #include "ui/gfx/color_utils.h"
 #include "ui/gfx/geometry/rect_conversions.h"
+#include "ui/gfx/scoped_canvas.h"
 #include "ui/gfx/screen.h"
 #include "ui/strings/grit/ui_strings.h"
 #include "ui/views/controls/button/menu_button.h"
@@ -551,13 +552,13 @@ BrowserView* BrowserView::GetBrowserViewForBrowser(const Browser* browser) {
 void BrowserView::Paint1pxHorizontalLine(gfx::Canvas* canvas,
                                          SkColor color,
                                          const gfx::Rect& bounds) {
-  const float scale = canvas->SaveAndUnscale();
+  gfx::ScopedCanvas scoped_canvas(canvas);
+  const float scale = canvas->UndoDeviceScaleFactor();
   gfx::RectF rect(gfx::ScaleRect(gfx::RectF(bounds), scale));
   rect.Inset(0, rect.height() - 1, 0, 0);
   SkPaint paint;
   paint.setColor(color);
   canvas->sk_canvas()->drawRect(gfx::RectFToSkRect(rect), paint);
-  canvas->Restore();
 }
 
 void BrowserView::InitStatusBubble() {

chrome/browser/ui/views/location_bar/location_bar_view.cc

@@ -1329,7 +1329,8 @@ void LocationBarView::PaintChildren(const ui::PaintContext& context) {
 
   if (ui::MaterialDesignController::IsModeMaterial()) {
     gfx::Canvas* canvas = recorder.canvas();
-    const float scale = canvas->SaveAndUnscale();
+    gfx::ScopedCanvas scoped_canvas(canvas);
+    const float scale = canvas->UndoDeviceScaleFactor();
 
     SkPaint paint;
     paint.setStyle(SkPaint::Style::kStroke_Style);
@@ -1346,7 +1347,6 @@ void LocationBarView::PaintChildren(const ui::PaintContext& context) {
     const SkScalar kCornerRadius = SkDoubleToScalar(2.5f * scale);
     canvas->sk_canvas()->drawRoundRect(gfx::RectFToSkRect(border_rect_f),
                                        kCornerRadius, kCornerRadius, paint);
-    recorder.canvas()->Restore();
   } else {
     views::Painter::PaintPainterAt(recorder.canvas(), border_painter_.get(),
                                    border_rect);

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);
 }

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

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

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_;