ui/gfx: remove redundant erase operations and remove unused function

It removes erase operations for SkBitmaps
which touch whole inside pixels
since all pixels should be drawn fully.

Additionally, it removes a unused function, CreateSuperimposedBitmap().

BUG=NONE
TEST=gfx_unittests --gtest_filter="SkBitmapOperationsTest*"

Review URL: https://codereview.chromium.org/394183002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@283814 0039d316-1c4b-4281-b951-d872f2087c98

ui/gfx/skbitmap_operations.cc

@@ -27,7 +27,6 @@ SkBitmap SkBitmapOperations::CreateInvertedBitmap(const SkBitmap& image) {
 
   SkBitmap inverted;
   inverted.allocN32Pixels(image.width(), image.height());
-  inverted.eraseARGB(0, 0, 0, 0);
 
   for (int y = 0; y < image.height(); ++y) {
     uint32* image_row = image.getAddr32(0, y);
@@ -43,35 +42,6 @@ SkBitmap SkBitmapOperations::CreateInvertedBitmap(const SkBitmap& image) {
   return inverted;
 }
 
-// static
-SkBitmap SkBitmapOperations::CreateSuperimposedBitmap(const SkBitmap& first,
-                                                      const SkBitmap& second) {
-  DCHECK(first.width() == second.width());
-  DCHECK(first.height() == second.height());
-  DCHECK(first.bytesPerPixel() == second.bytesPerPixel());
-  DCHECK(first.colorType() == kN32_SkColorType);
-
-  SkAutoLockPixels lock_first(first);
-  SkAutoLockPixels lock_second(second);
-
-  SkBitmap superimposed;
-  superimposed.allocN32Pixels(first.width(), first.height());
-  superimposed.eraseARGB(0, 0, 0, 0);
-
-  SkCanvas canvas(superimposed);
-
-  SkRect rect;
-  rect.fLeft = 0;
-  rect.fTop = 0;
-  rect.fRight = SkIntToScalar(first.width());
-  rect.fBottom = SkIntToScalar(first.height());
-
-  canvas.drawBitmapRect(first, NULL, rect);
-  canvas.drawBitmapRect(second, NULL, rect);
-
-  return superimposed;
-}
-
 // static
 SkBitmap SkBitmapOperations::CreateBlendedBitmap(const SkBitmap& first,
                                                  const SkBitmap& second,
@@ -95,7 +65,6 @@ SkBitmap SkBitmapOperations::CreateBlendedBitmap(const SkBitmap& first,
 
   SkBitmap blended;
   blended.allocN32Pixels(first.width(), first.height());
-  blended.eraseARGB(0, 0, 0, 0);
 
   double first_alpha = 1 - alpha;
 
@@ -135,7 +104,6 @@ SkBitmap SkBitmapOperations::CreateMaskedBitmap(const SkBitmap& rgb,
 
   SkBitmap masked;
   masked.allocN32Pixels(rgb.width(), rgb.height());
-  masked.eraseARGB(0, 0, 0, 0);
 
   SkAutoLockPixels lock_rgb(rgb);
   SkAutoLockPixels lock_alpha(alpha);
@@ -551,7 +519,6 @@ SkBitmap SkBitmapOperations::CreateHSLShiftedBitmap(
 
   SkBitmap shifted;
   shifted.allocN32Pixels(bitmap.width(), bitmap.height());
-  shifted.eraseARGB(0, 0, 0, 0);
 
   SkAutoLockPixels lock_bitmap(bitmap);
   SkAutoLockPixels lock_shifted(shifted);
@@ -575,7 +542,6 @@ SkBitmap SkBitmapOperations::CreateTiledBitmap(const SkBitmap& source,
 
   SkBitmap cropped;
   cropped.allocN32Pixels(dst_w, dst_h);
-  cropped.eraseARGB(0, 0, 0, 0);
 
   SkAutoLockPixels lock_source(source);
   SkAutoLockPixels lock_cropped(cropped);

ui/gfx/skbitmap_operations.h

@@ -32,12 +32,6 @@ class GFX_EXPORT SkBitmapOperations {
   // (0, 240, 255). The alpha value is not inverted.
   static SkBitmap CreateInvertedBitmap(const SkBitmap& image);
 
-  // Create a bitmap that is a superimposition of the second bitmap on top of
-  // the first. The provided bitmaps must use have the kARGB_8888_Config config
-  // and be of equal dimensions.
-  static SkBitmap CreateSuperimposedBitmap(const SkBitmap& first,
-                                           const SkBitmap& second);
-
   // Create a bitmap that is a blend of two others. The alpha argument
   // specifies the opacity of the second bitmap. The provided bitmaps must
   // use have the kARGB_8888_Config config and be of equal dimensions.