[MIPS] Add chromium.runtime API support for Loongson.

Extension API tests chromium.runtime GetPlatformInfo functions return NULL.
Bug comes from automated test unit: browser_tests

BUG= 838783
R= tbarzic@chromium.org

Change-Id: I4f6b04835fb949f15218c5adc4401950ba14b0a3
Reviewed-on: https://chromium-review.googlesource.com/1038912Reviewed-by: Devlin <rdevlin.cronin@chromium.org>
Commit-Queue: 汪 清 <wangqing-hf@loongson.cn>
Cr-Commit-Position: refs/heads/master@{#555957}

chrome/browser/extensions/api/runtime/chrome_runtime_api_delegate.cc

@@ -283,6 +283,10 @@ bool ChromeRuntimeAPIDelegate::GetPlatformInfo(PlatformInfo* info) {
     info->arch = extensions::api::runtime::PLATFORM_ARCH_X86_32;
   } else if (strcmp(arch, "x64") == 0) {
     info->arch = extensions::api::runtime::PLATFORM_ARCH_X86_64;
+  } else if (strcmp(arch, "mipsel") == 0) {
+    info->arch = extensions::api::runtime::PLATFORM_ARCH_MIPS;
+  } else if (strcmp(arch, "mips64el") == 0) {
+    info->arch = extensions::api::runtime::PLATFORM_ARCH_MIPS64;
   } else {
     NOTREACHED();
     return false;
@@ -295,6 +299,10 @@ bool ChromeRuntimeAPIDelegate::GetPlatformInfo(PlatformInfo* info) {
     info->nacl_arch = extensions::api::runtime::PLATFORM_NACL_ARCH_X86_32;
   } else if (strcmp(nacl_arch, "x86-64") == 0) {
     info->nacl_arch = extensions::api::runtime::PLATFORM_NACL_ARCH_X86_64;
+  } else if (strcmp(nacl_arch, "mips32") == 0) {
+    info->nacl_arch = extensions::api::runtime::PLATFORM_NACL_ARCH_MIPS;
+  } else if (strcmp(nacl_arch, "mips64") == 0) {
+    info->nacl_arch = extensions::api::runtime::PLATFORM_NACL_ARCH_MIPS64;
   } else {
     NOTREACHED();
     return false;

extensions/common/api/runtime.json

@@ -71,14 +71,14 @@
       {
         "id": "PlatformArch",
         "type": "string",
-        "enum": ["arm", "x86-32", "x86-64"],
+        "enum": ["arm", "x86-32", "x86-64", "mips", "mips64"],
         "description": "The machine's processor architecture."
       },
       {
         "id": "PlatformNaclArch",
         "description": "The native client architecture. This may be different from arch on some platforms.",
         "type": "string",
-        "enum": ["arm", "x86-32", "x86-64"]
+        "enum": ["arm", "x86-32", "x86-64", "mips", "mips64"]
       },
       {
         "id": "PlatformInfo",