Reland: Add ETC1 powered SSE encoder for tile texture compression

cc/resources/texture_compressor.cc

 // Copyright 2015 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 "cc/resources/texture_compressor.h"
 
+#include "base/cpu.h"

[reveman, 2015/05/06 18:44:00]

nit: guard this with a ifdef as it's not always used

[radu.velea, 2015/05/07 11:21:39]

Done.

 #include "base/logging.h"
 #include "cc/resources/texture_compressor_etc1.h"
+#include "cc/resources/texture_compressor_etc1_sse.h"

[reveman, 2015/05/06 18:44:00]

nit: guard this with a ifdef as it's not always used

[radu.velea, 2015/05/07 11:21:39]

Done.

 
 namespace cc {
 
 scoped_ptr<TextureCompressor> TextureCompressor::Create(Format format) {
   switch (format) {
-    case kFormatETC1:
+    case kFormatETC1: {
+#if defined(__i386__) || defined(__x86_64__)

[reveman, 2015/05/06 18:44:00]

Can you add a define to the build files and use it here instead? That would
avoid the chance of this somehow getting out of sync. 

[radu.velea, 2015/05/07 11:21:39]

-msse2 sets __SSE2__ would this be enough for the ifguards of both the headers
and this section? I see it is used elsewhere inside Chrome.

Otherwise I can add something like -DUSE_SSE_COMPRESSION in the build files and
replace __SSE2__ with that.

+      base::CPU cpu;
+      if (cpu.has_sse2()) {
+        return make_scoped_ptr(new TextureCompressorETC1SSE());
+      }
+#endif
       return make_scoped_ptr(new TextureCompressorETC1());
+    }
   }
 
   NOTREACHED();
   return nullptr;
 }
 
 }  // namespace cc