Create EarlGrey wait utility.

ios/web/public/test/web_view_interaction_test_util.mm

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #import "ios/web/public/test/web_view_interaction_test_util.h"
 
 #import <Foundation/Foundation.h>
 
 #include "base/mac/bind_objc_block.h"
 #include "base/strings/stringprintf.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/test/ios/wait_util.h"
 #include "ios/testing/earl_grey/wait_util.h"
 
 using web::NavigationManager;
 
 namespace web {
 namespace test {
 
 void TapWebViewElementWithId(web::WebState* web_state,
                              const std::string& element_id) {
   const char kJsClick[] = "document.getElementById('%s').click()";
   __block bool did_complete = false;
   web_state->ExecuteJavaScript(
       base::UTF8ToUTF16(base::StringPrintf(kJsClick, element_id.c_str())),
       base::BindBlock(^(const base::Value*) {
         did_complete = true;
       }));
 
-  // TODO(crbug.com/610837): Re-factor wait code into common location.
-  NSDate* deadline = [NSDate
-      dateWithTimeIntervalSinceNow:testing::kWaitForJSCompletionTimeout];
-  while (([[NSDate date] compare:deadline] != NSOrderedDescending) &&
-         !did_complete) {
-    base::test::ios::SpinRunLoopWithMaxDelay(
-        base::TimeDelta::FromSecondsD(testing::kSpinDelaySeconds));
-  }
+  testing::WaitUntilCondition(testing::kWaitForJSCompletionTimeout, ^() {

[Eugene But (OOO till 7-30), 2016/06/06 21:38:59]

Optional NIT: s/^() {/^{

[baxley, 2016/06/06 22:38:07]

Done.

+    return did_complete;
+  });

[baxley, 2016/06/06 21:20:48]

Let me know what you think of the readability here and if a variable for the
block would be useful. It wouldn't shorten the number of lines, though it may
make it more readable.

[Eugene But (OOO till 7-30), 2016/06/06 21:38:59]

I believe that inline blocks are more readable comparing to using a local
variable for them. This is because Actual code flow is Call Method -> Call block
and local variable reverses this order.

Sometimes however inline blocks make formatting unreadable, but this is
definitely not the case!

[baxley, 2016/06/06 22:38:07]

Acknowledged.

 }
 
 }  // namespace test
 }  // namespace web