Use the new DrawHighlight() helper to replace GlowHoverController::Draw().

chrome/browser/ui/views/tabs/tab.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/ui/views/tabs/tab.h"
 
 #include <limits>
 
 #include "base/command_line.h"
 #include "base/debug/alias.h"
@@ skipping 1207 matching lines @@
   // should be at the top of the tab. Otherwise, we assume that the background
   // image is a composited foreground + frame image.
   const int y_offset = GetThemeProvider()->HasCustomImage(tab_id) ?
       0 : background_offset_.y();
 
   const gfx::Insets tab_insets(GetLayoutInsets(TAB));
   // Don't draw over the toolbar, but do include the 1 px divider stroke at the
   // bottom.
   const int toolbar_overlap = tab_insets.bottom() - 1;
 
+  const SkScalar radius = SkFloatToScalar(width() / 3.f);
+  const bool draw_hover = hover_controller_.ShouldDraw() && radius > 0;
+  SkPoint hover_location(PointToSkPoint(hover_controller_.location()));
+  const SkAlpha hover_alpha = hover_controller_.GetAlpha();

[Peter Kasting, 2015/11/04 23:47:10]

If you're wondering why this block is way up here and not down below, it's
because my next change is going to refactor code such that we can avoid creating
|background_canvas| in the next statement if we're not drawing the hover effect,
and instead just draw directly to |canvas|.

+
   // Draw everything to a temporary canvas so we can extract an image for use in
   // masking the hover glow.
   gfx::Canvas background_canvas(size(), canvas->image_scale(), false);
 
   // Draw left edge.
   gfx::ImageSkia tab_l = gfx::ImageSkiaOperations::CreateTiledImage(
       *tab_background, x_offset, y_offset, mask_images_.l_width, height());
   gfx::ImageSkia theme_l =
       gfx::ImageSkiaOperations::CreateMaskedImage(tab_l, *mask_images_.image_l);
   background_canvas.DrawImageInt(
@@ skipping 15 matching lines @@
   // it by incrementing by the top padding, since it's a simple rectangle.
   background_canvas.TileImageInt(
       *tab_background, x_offset + mask_images_.l_width,
       y_offset + tab_insets.top(), mask_images_.l_width, tab_insets.top(),
       width() - mask_images_.l_width - mask_images_.r_width,
       height() - tab_insets.top() - toolbar_overlap);
 
   gfx::ImageSkia background_image(background_canvas.ExtractImageRep());
   canvas->DrawImageInt(background_image, 0, 0);
 
-  if (!GetThemeProvider()->HasCustomImage(tab_id) &&
-      hover_controller_.ShouldDraw())
-    hover_controller_.Draw(canvas, background_image);
+  if (draw_hover) {
+    gfx::Canvas hover_canvas(size(), canvas->image_scale(), false);
+    DrawHighlight(&hover_canvas, hover_location, radius, hover_alpha);
+    gfx::ImageSkia result = gfx::ImageSkiaOperations::CreateMaskedImage(
+        gfx::ImageSkia(hover_canvas.ExtractImageRep()), background_image);
+    canvas->DrawImageInt(result, 0, 0);
+  }
 
   // Now draw the stroke, highlights, and shadows around the tab edge.
   TabImages* stroke_images = &inactive_images_;
   canvas->DrawImageInt(*stroke_images->image_l, 0, 0);
   canvas->TileImageInt(
       *stroke_images->image_c, stroke_images->l_width, 0,
       width() - stroke_images->l_width - stroke_images->r_width, height());
   canvas->DrawImageInt(*stroke_images->image_r,
                        width() - stroke_images->r_width, 0);
 }
@@ skipping 306 matching lines @@
                          const gfx::ImageSkia& image) {
   DCHECK_NE(scale_factor, ui::SCALE_FACTOR_NONE);
   ImageCacheEntry entry;
   entry.resource_id = resource_id;
   entry.scale_factor = scale_factor;
   entry.image = image;
   image_cache_->push_front(entry);
   if (image_cache_->size() > kMaxImageCacheSize)
     image_cache_->pop_back();
 }