Minor optimization for tab capture on Aura.

When the scaling is FAST (the default) and MRT is enabled, just skip the scaling step as the
first step in the MRT pipeline is fully capable of doing a bilinear scale already.

BUG=284550

Review URL: https://codereview.chromium.org/48903007

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@231653 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 18 insertions, 4 deletions

diff --git a/content/common/gpu/client/gl_helper.cc b/content/common/gpu/client/gl_helper.cc
index dd39347..c8d57ac 100644
--- a/content/common/gpu/client/gl_helper.cc
+++ b/content/common/gpu/client/gl_helper.cc
@@ -284,6 +284,7 @@ class GLHelper::CopyTextureToImpl :
     CopyTextureToImpl* copy_impl_;
     gfx::Size dst_size_;
     gfx::Rect dst_subrect_;
+    GLHelper::ScalerQuality quality_;
     ScalerHolder scaler_;
     scoped_ptr<content::GLHelperScaling::ShaderInterface> pass1_shader_;
     scoped_ptr<content::GLHelperScaling::ShaderInterface> pass2_shader_;
@@ -891,6 +892,7 @@ GLHelper::CopyTextureToImpl::ReadbackYUV_MRT::ReadbackYUV_MRT(
       copy_impl_(copy_impl),
       dst_size_(dst_size),
       dst_subrect_(dst_subrect),
+      quality_(quality),
       scaler_(context, scaler_impl->CreateScaler(
           quality,
           src_size,
@@ -952,15 +954,27 @@ void GLHelper::CopyTextureToImpl::ReadbackYUV_MRT::ReadbackYUV(
   WebGLId mailbox_texture =
       copy_impl_->ConsumeMailboxToTexture(mailbox, sync_point);
 
-  // Scale texture to right size.
-  scaler_.Scale(mailbox_texture);
-  context_->deleteTexture(mailbox_texture);
+  WebGLId texture;
+  if (quality_ == GLHelper::SCALER_QUALITY_FAST) {
+    // Optimization: SCALER_QUALITY_FAST is just a single bilinear
+    // pass, which pass1_shader_ can do just as well, so let's skip
+    // the actual scaling in that case.
+    texture = mailbox_texture;
+  } else {
+    // Scale texture to right size.
+    scaler_.Scale(mailbox_texture);
+    texture = scaler_.texture();
+  }
+
 
   std::vector<WebKit::WebGLId> outputs(2);
   // Convert the scaled texture in to Y, U and V planes.
   outputs[0] = y_.texture();
   outputs[1] = uv_;
-  pass1_shader_->Execute(scaler_.texture(), outputs);
+  pass1_shader_->Execute(texture, outputs);
+
+  context_->deleteTexture(mailbox_texture);
+
   outputs[0] = u_.texture();
   outputs[1] = v_.texture();
   pass2_shader_->Execute(uv_, outputs);