Migrate 'Win ASan Release Media' builder to x64.

R=bpastene@chromium.org

Bug: 968862
Change-Id: I28c04c9ba7e7d919d4bca7c07e5785ed7afc2bdc
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1638121
Commit-Queue: Abhishek Arya <inferno@chromium.org>
Commit-Queue: John Budorick <jbudorick@chromium.org>
Auto-Submit: Abhishek Arya <inferno@chromium.org>
Reviewed-by: John Budorick <jbudorick@chromium.org>
Cr-Commit-Position: refs/heads/master@{#665027}

tools/mb/mb_config.pyl

@@ -195,7 +195,7 @@
       'TSAN Release': 'tsan_disable_nacl_release_bot',
       'UBSan Release': 'ubsan_release_bot',
       'UBSan vptr Release': 'ubsan_vptr_release_bot',
-      'Win ASan Release Media': 'asan_fuzzer_v8_heap_chrome_with_codecs_release_bot_x86',
+      'Win ASan Release Media': 'asan_fuzzer_v8_heap_chrome_with_codecs_release_bot',
       'Win ASan Release': 'asan_fuzzer_v8_heap_release_bot',
     },
 
@@ -440,7 +440,7 @@
       'TSAN Release': 'tsan_disable_nacl_release_bot',
       'UBSan Release': 'ubsan_release_bot',
       'UBSan vptr Release': 'ubsan_vptr_release_bot',
-      'Win ASan Release Media': 'asan_fuzzer_v8_heap_chrome_with_codecs_release_bot_x86',
+      'Win ASan Release Media': 'asan_fuzzer_v8_heap_chrome_with_codecs_release_bot',
       'Win ASan Release': 'asan_fuzzer_v8_heap_release_bot',
     },
 
@@ -1147,8 +1147,8 @@
       'asan', 'minimal_symbols', 'disable_nacl', 'release_bot', 'dcheck_always_on',
     ],
 
-    'asan_fuzzer_v8_heap_chrome_with_codecs_release_bot_x86': [
-      'clang', 'asan', 'fuzzer', 'v8_heap', 'chrome_with_codecs', 'release_bot', 'x86',
+    'asan_fuzzer_v8_heap_chrome_with_codecs_release_bot': [
+      'clang', 'asan', 'fuzzer', 'v8_heap', 'chrome_with_codecs', 'release_bot',
     ],
 
     'asan_fuzzer_v8_heap_release_bot': [