gpu: Don't clear texture level in DoCopyTexSubImage2D() if not needed.

gpu/command_buffer/service/gles2_cmd_decoder_unittest_textures.cc

 // Copyright 2014 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 "gpu/command_buffer/service/gles2_cmd_decoder.h"
 
 #include "base/command_line.h"
 #include "base/strings/string_number_conversions.h"
 #include "gpu/command_buffer/common/gles2_cmd_format.h"
 #include "gpu/command_buffer/common/gles2_cmd_utils.h"
@@ skipping 1785 matching lines @@
                                 GL_RGBA,
                                 GL_UNSIGNED_BYTE,
                                 2,
                                 2);
   EXPECT_CALL(*gl_, CopyTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, 0, 0, 1, 1))
       .Times(1)
       .RetiresOnSaturation();
   CopyTexSubImage2D cmd;
   cmd.Init(GL_TEXTURE_2D, 0, 0, 0, 0, 0, 1, 1);
   EXPECT_EQ(error::kNoError, ExecuteCmd(cmd));
+
+  TextureManager* manager = group().texture_manager();
+  TextureRef* texture_ref = manager->GetTexture(client_texture_id_);
+  ASSERT_TRUE(texture_ref != NULL);
+  Texture* texture = texture_ref->texture();
+  EXPECT_TRUE(texture->SafeToRenderFrom());
+}
+
+TEST_P(GLES2DecoderTest, CopyTexSubImage2DClearsUnclearedBackBufferSizedTexture) {
+  DoBindTexture(GL_TEXTURE_2D, client_texture_id_, kServiceTextureId);
+  DoTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, kBackBufferWidth, kBackBufferHeight,
+               0, GL_RGBA, GL_UNSIGNED_BYTE, 0, 0);
+
+  EXPECT_CALL(*gl_, CopyTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, 0, 0,
+                                      kBackBufferWidth, kBackBufferHeight))
+      .Times(1)
+      .RetiresOnSaturation();
+  CopyTexSubImage2D cmd;
+  cmd.Init(GL_TEXTURE_2D, 0, 0, 0, 0, 0, kBackBufferWidth, kBackBufferHeight);
+  EXPECT_EQ(error::kNoError, ExecuteCmd(cmd));
+
+  TextureManager* manager = group().texture_manager();
+  TextureRef* texture_ref = manager->GetTexture(client_texture_id_);
+  ASSERT_TRUE(texture_ref != NULL);
+  Texture* texture = texture_ref->texture();
+  EXPECT_TRUE(texture->SafeToRenderFrom());
 }
 
 TEST_P(GLES2DecoderManualInitTest, CompressedImage2DMarksTextureAsCleared) {
   InitState init;
   init.extensions = "GL_EXT_texture_compression_s3tc";
   init.gl_version = "3.0";
   init.bind_generates_resource = true;
   InitDecoder(init);
 
   DoBindTexture(GL_TEXTURE_2D, client_texture_id_, kServiceTextureId);
@@ skipping 1017 matching lines @@
 // TODO(gman): CompressedTexSubImage2DImmediate
 
 // TODO(gman): TexImage2D
 
 // TODO(gman): TexImage2DImmediate
 
 // TODO(gman): TexSubImage2DImmediate
 
 }  // namespace gles2
 }  // namespace gpu