Update from https://crrev.com/303153

third_party/boringssl/BUILD.gn

Index: third_party/boringssl/BUILD.gn
diff --git a/third_party/boringssl/BUILD.gn b/third_party/boringssl/BUILD.gn
index 5dffa6506149907c0473f8f82932d8571129776e..ccd842451dd4fc55002067eea93f5ad3527b460c 100644
--- a/third_party/boringssl/BUILD.gn
+++ b/third_party/boringssl/BUILD.gn
@@ -25,11 +25,16 @@ gypi_values = exec_script(
     "scope",
     [ "//third_party/boringssl/boringssl.gypi" ])
 
-# Win32's assembly is built by Yasm. The other ports use the platform assembler.
-if (cpu_arch == "x86" && is_win) {
+# Windows' assembly is built with Yasm. The other platforms use the platform
+# assembler.
+if (is_win) {
   import("//third_party/yasm/yasm_assemble.gni")
   yasm_assemble("boringssl_asm") {
-    sources = gypi_values.boringssl_win_x86_sources
+    if (cpu_arch == "x64") {
+      sources = gypi_values.boringssl_win_x86_64_sources
+    } else if (cpu_arch == "x86") {
+      sources = gypi_values.boringssl_win_x86_sources
+    }
   }
 }
 
@@ -61,13 +66,19 @@ component("boringssl") {
     "src/crypto",
   ]
 
+  if (is_win) {
+    # TODO(davidben): Fix size_t truncations in BoringSSL.
+    # https://crbug.com/429039
+    cflags += [ "/wd4267"]
+  }
+
   if (cpu_arch == "x64") {
     if (is_mac) {
       sources += gypi_values.boringssl_mac_x86_64_sources
     } else if (is_linux || is_android) {
       sources += gypi_values.boringssl_linux_x86_64_sources
     } else if (is_win) {
-      sources += gypi_values.boringssl_win_x86_64_sources
+      deps += [ ":boringssl_asm" ]
     } else {
       defines += [ "OPENSSL_NO_ASM" ]
     }