Support an ALPHA_8 UIResourceBitmap format

Add an ALPHA_8 UIResourceFormat corresponding to the kAlpha_8_SkColorType. Also
plumb this format to its corresponding ALPHA_8 OpenGL format. This is in
preparation for the UIResource-backed Android L overscroll effect,
https://codereview.chromium.org/367173003/.

BUG=389744

Review URL: https://codereview.chromium.org/463663002

Cr-Commit-Position: refs/heads/master@{#289428}
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@289428 0039d316-1c4b-4281-b951-d872f2087c98

cc/resources/resource_format.cc

@@ -14,6 +14,7 @@ SkColorType ResourceFormatToSkColorType(ResourceFormat format) {
     case BGRA_8888:
       return kN32_SkColorType;
     case ETC1:
+    case ALPHA_8:
     case LUMINANCE_8:
     case RGB_565:
       NOTREACHED();

cc/resources/resource_format.h

@@ -15,6 +15,7 @@ enum ResourceFormat {
   RGBA_8888,
   RGBA_4444,
   BGRA_8888,
+  ALPHA_8,
   LUMINANCE_8,
   RGB_565,
   ETC1,

cc/resources/resource_provider.cc

@@ -70,6 +70,7 @@ GLenum TextureToStorageFormat(ResourceFormat format) {
       storage_format = GL_BGRA8_EXT;
       break;
     case RGBA_4444:
+    case ALPHA_8:
     case LUMINANCE_8:
     case RGB_565:
     case ETC1:
@@ -86,6 +87,7 @@ bool IsFormatSupportedForStorage(ResourceFormat format) {
     case BGRA_8888:
       return true;
     case RGBA_4444:
+    case ALPHA_8:
     case LUMINANCE_8:
     case RGB_565:
     case ETC1:
@@ -516,6 +518,7 @@ SkCanvas* ResourceProvider::BitmapRasterBuffer::DoLockForWrite() {
       raster_bitmap_.installPixels(info, mapped_buffer_, stride);
       break;
     }
+    case ALPHA_8:
     case LUMINANCE_8:
     case RGB_565:
     case ETC1:

cc/resources/resource_provider.h

@@ -663,6 +663,7 @@ inline unsigned BitsPerPixel(ResourceFormat format) {
     32,  // RGBA_8888
     16,  // RGBA_4444
     32,  // BGRA_8888
+    8,   // ALPHA_8
     8,   // LUMINANCE_8
     16,  // RGB_565,
     4    // ETC1
@@ -676,6 +677,7 @@ inline GLenum GLDataType(ResourceFormat format) {
     GL_UNSIGNED_BYTE,           // RGBA_8888
     GL_UNSIGNED_SHORT_4_4_4_4,  // RGBA_4444
     GL_UNSIGNED_BYTE,           // BGRA_8888
+    GL_UNSIGNED_BYTE,           // ALPHA_8
     GL_UNSIGNED_BYTE,           // LUMINANCE_8
     GL_UNSIGNED_SHORT_5_6_5,    // RGB_565,
     GL_UNSIGNED_BYTE            // ETC1
@@ -689,6 +691,7 @@ inline GLenum GLDataFormat(ResourceFormat format) {
     GL_RGBA,           // RGBA_8888
     GL_RGBA,           // RGBA_4444
     GL_BGRA_EXT,       // BGRA_8888
+    GL_ALPHA,          // ALPHA_8
     GL_LUMINANCE,      // LUMINANCE_8
     GL_RGB,            // RGB_565
     GL_ETC1_RGB8_OES   // ETC1

cc/resources/texture_uploader_unittest.cc

@@ -217,6 +217,15 @@ TEST(TextureUploaderTest, UploadContentsTest) {
   }
   UploadTexture(uploader.get(), RGBA_8888, gfx::Size(41, 43), buffer);
 
+  // Upload a tightly packed 41x86 ALPHA texture.
+  memset(buffer, 0, sizeof(buffer));
+  for (int i = 0; i < 86; ++i) {
+    // Mark the beginning and end of each row, for the test.
+    buffer[i * 1 * 41] = 0x1;
+    buffer[(i + 1) * 41 - 1] = 0x2;
+  }
+  UploadTexture(uploader.get(), ALPHA_8, gfx::Size(41, 86), buffer);
+
   // Upload a tightly packed 82x86 LUMINANCE texture.
   memset(buffer, 0, sizeof(buffer));
   for (int i = 0; i < 86; ++i) {

cc/resources/ui_resource_bitmap.cc

@@ -11,6 +11,26 @@
 #include "third_party/skia/include/core/SkPixelRef.h"
 
 namespace cc {
+namespace {
+
+UIResourceBitmap::UIResourceFormat SkColorTypeToUIResourceFormat(
+    SkColorType sk_type) {
+  UIResourceBitmap::UIResourceFormat format = UIResourceBitmap::RGBA8;
+  switch (sk_type) {
+    case kN32_SkColorType:
+      format = UIResourceBitmap::RGBA8;
+      break;
+    case kAlpha_8_SkColorType:
+      format = UIResourceBitmap::ALPHA_8;
+      break;
+    default:
+      NOTREACHED() << "Invalid SkColorType for UIResourceBitmap: " << sk_type;
+      break;
+  }
+  return format;
+}
+
+}  // namespace
 
 void UIResourceBitmap::Create(const skia::RefPtr<SkPixelRef>& pixel_ref,
                               const gfx::Size& size,
@@ -29,14 +49,14 @@ void UIResourceBitmap::Create(const skia::RefPtr<SkPixelRef>& pixel_ref,
 }
 
 UIResourceBitmap::UIResourceBitmap(const SkBitmap& skbitmap) {
-  DCHECK_EQ(skbitmap.colorType(), kN32_SkColorType);
   DCHECK_EQ(skbitmap.width(), skbitmap.rowBytesAsPixels());
   DCHECK(skbitmap.isImmutable());
 
   skia::RefPtr<SkPixelRef> pixel_ref = skia::SharePtr(skbitmap.pixelRef());
   const SkImageInfo& info = pixel_ref->info();
-  Create(
-      pixel_ref, gfx::Size(info.fWidth, info.fHeight), UIResourceBitmap::RGBA8);
+  Create(pixel_ref,
+         gfx::Size(info.fWidth, info.fHeight),
+         SkColorTypeToUIResourceFormat(skbitmap.colorType()));
 
   SetOpaque(skbitmap.isOpaque());
 }

cc/resources/ui_resource_bitmap.h

@@ -27,6 +27,7 @@ class CC_EXPORT UIResourceBitmap {
  public:
   enum UIResourceFormat {
     RGBA8,
+    ALPHA_8,
     ETC1
   };
   enum UIResourceWrapMode {
@@ -42,7 +43,7 @@ class CC_EXPORT UIResourceBitmap {
   void SetOpaque(bool opaque) { opaque_ = opaque; }
 
   // User must ensure that |skbitmap| is immutable.  The SkBitmap Format should
-  // be 32-bit RGBA.
+  // be 32-bit RGBA or 8-bit ALPHA.
   explicit UIResourceBitmap(const SkBitmap& skbitmap);
   UIResourceBitmap(const gfx::Size& size, bool is_opaque);
   UIResourceBitmap(const skia::RefPtr<SkPixelRef>& pixel_ref,

cc/trees/layer_tree_host_impl.cc

@@ -3284,8 +3284,16 @@ void LayerTreeHostImpl::CreateUIResource(UIResourceId uid,
     DeleteUIResource(uid);
 
   ResourceFormat format = resource_provider_->best_texture_format();
-  if (bitmap.GetFormat() == UIResourceBitmap::ETC1)
-    format = ETC1;
+  switch (bitmap.GetFormat()) {
+    case UIResourceBitmap::RGBA8:
+      break;
+    case UIResourceBitmap::ALPHA_8:
+      format = ALPHA_8;
+      break;
+    case UIResourceBitmap::ETC1:
+      format = ETC1;
+      break;
+  };
   id = resource_provider_->CreateResource(
       bitmap.GetSize(),
       wrap_mode,

content/browser/compositor/overlay_candidate_validator_ozone.cc

@@ -15,6 +15,7 @@ static ui::SurfaceFactoryOzone::BufferFormat GetOzoneFormat(
       return ui::SurfaceFactoryOzone::RGBA_8888;
     case cc::RGBA_4444:
     case cc::BGRA_8888:
+    case cc::ALPHA_8:
     case cc::LUMINANCE_8:
     case cc::RGB_565:
     case cc::ETC1:

mojo/services/public/interfaces/surfaces/surfaces.mojom

@@ -13,6 +13,7 @@ enum ResourceFormat {
   RGBA_8888,
   RGBA_4444,
   BGRA_8888,
+  ALPHA_8,
   LUMINANCE_8,
   RGB_565,
   ETC1,