GN rules for libwebp dsp neon stuff

This stuff is needed to get blink linking in android.

R=brettw@chromium.org,fbarchard@chromium.org

Review URL: https://codereview.chromium.org/541953002

Cr-Commit-Position: refs/heads/master@{#293668}

third_party/libwebp/BUILD.gn

@@ -2,10 +2,16 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+import("//build/config/arm.gni")
+
 config("libwebp_config") {
   include_dirs = [ "." ]
 }
 
+use_dsp_neon = (cpu_arch == "arm64" ||
+            (cpu_arch == "arm" && arm_version >= 7 &&
+                (arm_use_neon || arm_optionally_use_neon)))
+
 source_set("libwebp_dec") {
   sources = [
     "dec/alpha.c",
@@ -25,13 +31,14 @@ source_set("libwebp_dec") {
 
   deps = [
     ":libwebp_dsp",
-# TODO(GYP):
-#    ":libwebp_dsp_neon",
     ":libwebp_utils",
   ]
   all_dependent_configs = [
     ":libwebp_config"
   ]
+  if (use_dsp_neon) {
+    deps += [ ":libwebp_dsp_neon"]
+  }
 }
 
 source_set("libwebp_demux") {
@@ -89,42 +96,28 @@ source_set("libwebp_dsp") {
 #      ],
 }
 
+if (use_dsp_neon) {
+
+source_set("libwebp_dsp_neon") {
+  sources = [
+    "dsp/dec_neon.c",
+    "dsp/enc_neon.c",
+    "dsp/lossless_neon.c",
+    "dsp/upsampling_neon.c",
+  ]
+
+  include_dirs = [ "." ]
+
+  if (cpu_arch == "arm") {
+    # behavior similar to *.c.neon in an Android.mk
+    configs -= [ "//build/config/compiler:compiler_arm_fpu" ]
+    cflags = [ "-mfpu=neon" ]
+  } else if (cpu_arch == "arm64") {
+    # avoid an ICE with gcc-4.9: b/15574841
+    cflags = [ "-frename-registers" ]
+  }
+
 # TODO(GYP):
-#    'variables': {
-#      'neon_sources': [
-#        "dsp/dec_neon.c",
-#        "dsp/enc_neon.c",
-#        "dsp/lossless_neon.c",
-#        "dsp/upsampling_neon.c",
-#      ]
-#    },
-#    {
-#      'target_name': 'libwebp_dsp_neon',
-#      'conditions': [
-#        ['target_arch == "arm" and arm_version >= 7 and (arm_neon == 1 or arm_neon_optional == 1)', {
-#          'type': 'static_library',
-#          'include_dirs': ['.'],
-#          'sources': [
-#            '<@(neon_sources)'
-#          ],
-#          # behavior similar to *.c.neon in an Android.mk
-#          'cflags!': [ '-mfpu=vfpv3-d16' ],
-#          'cflags': [ '-mfpu=neon' ],
-#        },{
-#          'conditions': [
-#            ['target_arch == "arm64"', {
-#              'type': 'static_library',
-#              'include_dirs': ['.'],
-#              'sources': [
-#                '<@(neon_sources)'
-#              ],
-#              # avoid an ICE with gcc-4.9: b/15574841
-#              'cflags': [ '-frename-registers' ],
-#            },{  # "target_arch != "arm|arm64" or arm_version < 7"
-#              'type': 'none',
-#            }],
-#          ],
-#        }],
 #        ['order_profiling != 0', {
 #          'target_conditions' : [
 #            ['_toolset=="target"', {
@@ -134,6 +127,9 @@ source_set("libwebp_dsp") {
 #        }],
 #      ],
 #    }
+}
+
+}  # use_dsp_neon
 
 source_set("libwebp_enc") {
   sources = [
@@ -194,12 +190,13 @@ group("libwebp") {
     ":libwebp_dec",
     ":libwebp_demux",
     ":libwebp_dsp",
-# TODO(GYP):
-#    ":libwebp_dsp_neon",
     ":libwebp_enc",
     ":libwebp_utils",
   ]
   direct_dependent_configs = [
     ":libwebp_config"
   ]
+  if (use_dsp_neon) {
+    deps += [ ":libwebp_dsp_neon" ]
+  }
 }