win: Let about:version list the C++ compiler used to build chrome.

We're hoping to send out a single clang-built canary later this week, and
this will be useful for identifying that.  After that, we can remove this
row again.

BUG=82385,530785

Review URL: https://codereview.chromium.org/1404063002

Cr-Commit-Position: refs/heads/master@{#353930}

chrome/browser/resources/about_version.html

@@ -100,6 +100,12 @@ about:version template page
           <td class="label" i18n-content="build_id_name"></td>
           <td class="version" i18n-content="build_id"></td>
         </tr>
+</if>
+<if expr="is_win">
+        <tr id="compiler-section">
+          <td class="label">Compiler</td>
+          <td class="version" id="compiler" i18n-content="compiler"></td>
+        </tr>
 </if>
       </table>
     </div>

chrome/browser/ui/webui/version_ui.cc

@@ -122,6 +122,14 @@ WebUIDataSource* CreateVersionUIDataSource() {
   html_source->AddLocalizedString("variations_name",
                                   IDS_ABOUT_VERSION_VARIATIONS);
 
+#if defined(OS_WIN)
+#if defined(__clang__)
+  html_source->AddString("compiler", "clang");
+#else
+  html_source->AddString("compiler", "MSVC");
+#endif
+#endif
+
   html_source->SetJsonPath("strings.js");
   html_source->AddResourcePath("version.js", IDR_ABOUT_VERSION_JS);
   html_source->AddResourcePath("about_version.css", IDR_ABOUT_VERSION_CSS);