[ChromeDriver] Add warning log massage for clear() element

Adding warning message for clear element calls.
Message warns the user that ChromeDriver 2.43 and above
has been updated to conform to the new W3C WebDriver specification.

Change-Id: I1bdad57c64d0697fcd3a12f71aaf984ce06c0d86
bug: chromedriver:2716
Reviewed-on: https://chromium-review.googlesource.com/c/1391868
Reviewed-by: John Chen <johnchen@chromium.org>
Commit-Queue: Artur Khachatryan <khachatryan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#622240}
diff --git a/chrome/test/chromedriver/element_commands.cc b/chrome/test/chromedriver/element_commands.cc
index 57043bf..46701ca 100644
--- a/chrome/test/chromedriver/element_commands.cc
+++ b/chrome/test/chromedriver/element_commands.cc
@@ -13,6 +13,7 @@
 #include "base/callback.h"
 #include "base/files/file_path.h"
 #include "base/files/file_util.h"
+#include "base/logging.h"
 #include "base/strings/string_split.h"
 #include "base/strings/stringprintf.h"
 #include "base/threading/platform_thread.h"
@@ -318,6 +319,16 @@
     }
     base::PlatformThread::Sleep(base::TimeDelta::FromMilliseconds(50));
   }
+  static bool isClearWarningNotified = false;
+  if (!isClearWarningNotified) {
+    std::string messageClearWarning =
+        "\n\t=== NOTE: ===\n"
+        "\tThe Clear command in ChromeDriver 2.43 and above\n"
+        "\thas been updated to conform to the current standard,\n"
+        "\tincluding raising blur event after clearing.\n";
+    VLOG(0) << messageClearWarning;
+    isClearWarningNotified = true;
+  }
   base::ListValue args;
   args.Append(CreateElement(element_id));
   std::unique_ptr<base::Value> result;