Update from https://crrev.com/303153

third_party/boringssl/boringssl.gyp

Index: third_party/boringssl/boringssl.gyp
diff --git a/third_party/boringssl/boringssl.gyp b/third_party/boringssl/boringssl.gyp
index c3760c061b015cdc3f5077ef94d65615a50c7aed..d0b716a8f7d43b348f336d69441f3bf34cb4d4eb 100644
--- a/third_party/boringssl/boringssl.gyp
+++ b/third_party/boringssl/boringssl.gyp
@@ -17,6 +17,9 @@
         'BORINGSSL_IMPLEMENTATION',
         'BORINGSSL_NO_STATIC_INITIALIZER',
       ],
+      # TODO(davidben): Fix size_t truncations in BoringSSL.
+      # https://crbug.com/429039
+      'msvs_disabled_warnings': [ 4267, ],
       'conditions': [
         ['component == "shared_library"', {
           'defines': [
@@ -36,8 +39,8 @@
             }],
             ['OS == "win"', {
               'sources': [ '<@(boringssl_win_x86_sources)' ],
-              # Win32 is built with Yasm. The other ports use the platform
-              # assembler.
+              # Windows' assembly is built with Yasm. The other platforms use
+              # the platform assembler.
               'variables': {
                 'yasm_output_path': '<(SHARED_INTERMEDIATE_DIR)/third_party/boringssl',
               },
@@ -60,6 +63,14 @@
             }],
             ['OS == "win"', {
               'sources': [ '<@(boringssl_win_x86_64_sources)' ],
+              # Windows' assembly is built with Yasm. The other platforms use
+              # the platform assembler.
+              'variables': {
+                'yasm_output_path': '<(SHARED_INTERMEDIATE_DIR)/third_party/boringssl',
+              },
+              'includes': [
+                '../yasm/yasm_compile.gypi',
+              ],
             }],
             ['OS != "mac" and OS != "linux" and OS != "win" and OS != "android"', {
               'defines': [ 'OPENSSL_NO_ASM' ],