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

This optimization is similar to one of TexSubImage2D().

TEST=Service/GLES2DecoderTest.CopyTexSubImage2DClearsUnclearedBackBufferSizedTexture

Review URL: https://codereview.chromium.org/824173003

Cr-Commit-Position: refs/heads/master@{#312371}

2 files changed, 37 insertions, 4 deletions

diff --git a/gpu/command_buffer/service/gles2_cmd_decoder.cc b/gpu/command_buffer/service/gles2_cmd_decoder.cc
index 0d778f3..f56d47b 100644
--- a/gpu/command_buffer/service/gles2_cmd_decoder.cc
+++ b/gpu/command_buffer/service/gles2_cmd_decoder.cc
@@ -9145,10 +9145,17 @@ void GLES2DecoderImpl::DoCopyTexSubImage2D(
   Clip(x, width, size.width(), &copyX, &copyWidth);
   Clip(y, height, size.height(), &copyY, &copyHeight);
 
-  if (!texture_manager()->ClearTextureLevel(this, texture_ref, target, level)) {
-    LOCAL_SET_GL_ERROR(
-        GL_OUT_OF_MEMORY, "glCopyTexSubImage2D", "dimensions too big");
-    return;
+  if (xoffset != 0 || yoffset != 0 || width != size.width() ||
+      height != size.height()) {
+    if (!texture_manager()->ClearTextureLevel(this, texture_ref, target,
+                                              level)) {
+      LOCAL_SET_GL_ERROR(GL_OUT_OF_MEMORY, "glCopyTexSubImage2D",
+                         "dimensions too big");
+      return;
+    }
+  } else {
+    // Write all pixels in below.
+    texture_manager()->SetLevelCleared(texture_ref, target, level, true);
   }
 
   if (copyX != x ||
diff --git a/gpu/command_buffer/service/gles2_cmd_decoder_unittest_textures.cc b/gpu/command_buffer/service/gles2_cmd_decoder_unittest_textures.cc
index b0e8e8c..f0cadf1 100644
--- a/gpu/command_buffer/service/gles2_cmd_decoder_unittest_textures.cc
+++ b/gpu/command_buffer/service/gles2_cmd_decoder_unittest_textures.cc
@@ -1803,6 +1803,32 @@ TEST_P(GLES2DecoderTest, CopyTexSubImage2DClearsUnclearedTexture) {
   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) {