Fix arch client hint sent with "request desktop site"

Just needs to be updated to match the spec changes --- it currently
bundles both x86 and x86-64 into "x86" hint value.

Bug: 1084527
Change-Id: Iec8074f420612ee406a3a82be747b0687c12b02a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2208536Reviewed-by: Yusuf Ozuysal <yusufo@chromium.org>
Commit-Queue: Maksim Orlovich <morlovich@chromium.org>
Cr-Commit-Position: refs/heads/master@{#770648}

chrome/android/javatests/src/org/chromium/chrome/browser/NavigateTest.java

@@ -309,7 +309,7 @@ public class NavigateTest {
                 tab.getWebContents(), "document.body.textContent");
         // Note: |content| is JSON, hence lots of escaping.
         Assert.assertEquals("Proper headers",
-                "\"\\\"x86_64\\\"\\n"
+                "\"\\\"x86\\\"\\n"
                         + "?0\\n"
                         + "\\\"\\\"\\n"
                         + "\\\"Linux\\\"\"",

chrome/browser/android/content/content_utils.cc

@@ -27,7 +27,7 @@ static void JNI_ContentUtils_SetUserAgentOverride(
   spoofed_ua.ua_metadata_override->platform = "Linux";
   spoofed_ua.ua_metadata_override->platform_version =
       std::string();  // match content::GetOSVersion(false) on Linux
-  spoofed_ua.ua_metadata_override->architecture = "x86_64";
+  spoofed_ua.ua_metadata_override->architecture = "x86";
   spoofed_ua.ua_metadata_override->model = std::string();
   spoofed_ua.ua_metadata_override->mobile = false;