Revert of Remove WebElement::hasTagName.

public/web/WebElement.h

Index: public/web/WebElement.h
diff --git a/public/web/WebElement.h b/public/web/WebElement.h
index a8d2414642142efee1e0a544ffd2195370fe192b..9308da0ad79f95aa555a77169d3f13420c4bdc40 100644
--- a/public/web/WebElement.h
+++ b/public/web/WebElement.h
@@ -54,6 +54,10 @@
         BLINK_EXPORT bool isTextFormControlElement() const;
         // Returns the qualified name, which may contain a prefix and a colon.
         BLINK_EXPORT WebString tagName() const;
+        // Check if this element has the specified qualified name. This function
+        // doesn't makes much sense because we have no ways to check namespace
+        // URI. Do not use this.
+        BLINK_EXPORT bool hasTagName(const WebString&) const;
         // Check if this element has the specified local tag name, and the HTML
         // namespace. Tag name matching is case-insensitive.
         BLINK_EXPORT bool hasHTMLTagName(const WebString&) const;