Add build targets for advanced Intel instruction sets (1 of 3).

CL (1 of 3) adds empty lists in our .gypi,
and builds the files in those empty lists with the appropriate flags.

CL (2 of 3) will have Chrome's GYP and GN files read these lists,
and build them with the appropriate flags.

CL (3 of 3) will add runtime detection and stub files to the lists
with empty Init_sse42(), Init_avx(), Init_avx2() methods.

After that, we should be able to use SSE 4.2, AVX, and AVX2 if desired.

Some motivation:
  - SSE 4.2 adds some sweet string-oriented methods that
    can help us write fast high quality 32-bit hashes.
  - AVX is SSE doubled, e.g. 8 floats or two SkPMFloat at a time.
  - AVX2 is SSE2 doubled, e.g. 8 pixels at a time.

BUG=skia:4117

Review URL: https://codereview.chromium.org/1290423007

1 files changed, 6 insertions, 0 deletions

diff --git a/gyp/opts.gypi b/gyp/opts.gypi
index eec677f484..d5dab44a45 100644
--- a/gyp/opts.gypi
+++ b/gyp/opts.gypi
@@ -52,4 +52,10 @@
             '<(skia_src_path)/opts/SkBlitRow_opts_SSE4.cpp',
             '<(skia_src_path)/opts/SkOpts_sse41.cpp',
         ],
+        'sse42_sources': [
+        ],
+        'avx_sources': [
+        ],
+        'avx2_sources': [
+        ],
 }