Improve DCHECK error message for web::ExecuteJavaScript.

ios/web/public/test/js_test_util.mm

Index: ios/web/public/test/js_test_util.mm
diff --git a/ios/web/public/test/js_test_util.mm b/ios/web/public/test/js_test_util.mm
index 00ab99d8776797c96f85963a093c90f63d1e11c6..b4ee0c405efb22b6d57361e728e576b97df2a5a3 100644
--- a/ios/web/public/test/js_test_util.mm
+++ b/ios/web/public/test/js_test_util.mm
@@ -8,7 +8,7 @@
 
 #include "base/logging.h"
 #import "base/mac/scoped_nsobject.h"
-#import "base/test/ios/wait_util.h"
+#import "ios/testing/wait_util.h"
 #import "ios/web/public/web_state/js/crw_js_injection_manager.h"
 #import "ios/web/public/web_state/js/crw_js_injection_receiver.h"
 
@@ -24,9 +24,12 @@ id ExecuteJavaScript(CRWJSInjectionManager* manager, NSString* script) {
              completed = true;
            }];
 
-  base::test::ios::WaitUntilCondition(^{
-    return completed;
-  });
+  BOOL success = testing::WaitUntilConditionOrTimeout(
+      testing::kWaitForJSCompletionTimeout, ^{
+        return completed;
+      });
+  DCHECK(success)

[Eugene But (OOO till 7-30), 2017/03/02 21:27:26]

Ideally we should not DCHECK in tests. Can we log instead?

[michaeldo, 2017/03/02 21:34:37]

We can log, however I didn't want to change the current behavior. (This
currently DCHECKS.) This will only hit if WKWebView doesn't call back as we
expect which isn't technically part of the test. I think it's an assumption that
this will complete in time, but of course the Javascript could be the issue
causing it not to return in time too. WDYT?

+      << "CRWJSInjectionManager failed to complete javascript execution.";
   return [[result retain] autorelease];
 }
 
@@ -50,9 +53,11 @@ id ExecuteJavaScript(WKWebView* web_view, NSString* script, NSError** error) {
                  *error = [[script_error copy] autorelease];
                completed = true;
              }];
-  base::test::ios::WaitUntilCondition(^{
-    return completed;
-  });
+  BOOL success = testing::WaitUntilConditionOrTimeout(
+      testing::kWaitForJSCompletionTimeout, ^{
+        return completed;
+      });
+  DCHECK(success) << "WKWebView failed to complete javascript execution.";
   return [[result retain] autorelease];
 }