[foozzie] Mock out performance.now

Also improve suppression of Math.pow precision.

BUG=chromium:679957
NOTRY=true
TBR=mstarzinger@chromium.org,jarin@chromium.org

Change-Id: I43d0cd6f6f6d0867be9f2337990114c07c716df5
Reviewed-on: https://chromium-review.googlesource.com/438327Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#42966}

tools/foozzie/v8_mock.js

@@ -51,6 +51,11 @@ var __PrettyPrint = function __PrettyPrint(msg) { print(msg); };
   Date = new Proxy(Date, handler);
 })();
 
+// Mock performace.now().
+(function () {
+  performance.now = function () { return 1.2; }
+})();
+
 // Mock stack traces.
 Error.prepareStackTrace = function (error, structuredStackTrace) {
   return "";

tools/foozzie/v8_suppressions.js

@@ -8,11 +8,13 @@
 // problem is fixed.
 
 // Suppress http://crbug.com/662429
-var __real_Math_pow = Math.pow
-Math.pow = function(a, b){
-  if (b < 0) {
-    return 0.000017;
-  } else {
-    return __real_Math_pow(a, b);
+(function () {
+  var __real_Math_pow = Math.pow
+  Math.pow = function(a, b){
+    if (b < 0) {
+      return 0.000017;
+    } else {
+      return __real_Math_pow(a, b);
+    }
   }
-}
+})();

tools/foozzie/v8_suppressions.py

@@ -78,8 +78,6 @@ IGNORE_SOURCES = {
 # TODO(machenbach): Insert a JS sentinel between the two parts, because
 # comments are stripped during minimization.
 IGNORE_TEST_CASES = {
-  'crbug.com/679957':
-      re.compile(r'.*performance\.now.*', re.S),
 }
 
 # Ignore by output pattern. Map from config->bug->regexp. Config '' is used