[ChromeDriver] Allow 0 for extensionLoadTimeout

The Chrome option extensionLoadTimeout should allow value of 0,
which means do not wait for extensions to load.

Bug: chromedriver:2329
Change-Id: I38de01f7c1facbbbd181cbd19ac6c710e379afb9
Reviewed-on: https://chromium-review.googlesource.com/963591Reviewed-by: Jonathon Kereliuk <kereliuk@chromium.org>
Commit-Queue: John Chen <johnchen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#543490}

chrome/test/chromedriver/capabilities.cc

@@ -66,10 +66,11 @@ Status ParseInterval(int* to_set,
 Status ParseTimeDelta(base::TimeDelta* to_set,
                       const base::Value& option,
                       Capabilities* capabilities) {
-  int milliseconds;
-  Status status = ParseInterval(&milliseconds, option, capabilities);
-  if (status.IsError())
-    return status;
+  int milliseconds = 0;
+  if (!option.GetAsInteger(&milliseconds))
+    return Status(kUnknownError, "must be an integer");
+  if (milliseconds < 0)
+    return Status(kUnknownError, "must be positive or zero");
   *to_set = base::TimeDelta::FromMilliseconds(milliseconds);
   return Status(kOk);
 }