Remove WebKit::toHTMLInputElement.

This function is a dupe of Node::toInputElement. We replace all callsites of
toHTMLInputElement with Node::toInputElement.

Note:
- findPasswordFormFields: Change hasLocalName to hasTagName. Checking only local
  tag name is dangerous in general. This change doesn't change any behavior
  because formElement is an element in the HTML namespace.

- autocompleteHandleKeyEvent: Ditto. Autofill UI woorks only with elements in
  the HTML namespace.

BUG=230618

Review URL: https://chromiumcodereview.appspot.com/14043003

git-svn-id: svn://svn.chromium.org/blink/trunk@148353 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Streamline the includes in HashTable.h

HashTable.h is included directly or indirectly in most Blink compilation units,
so it seems beneficial to remove some unneccessary includes that are not widely
required.

R=abarth@chromium.org
BUG=none
TEST=compiles debug+release, will use cq.

Review URL: https://chromiumcodereview.appspot.com/13951018

git-svn-id: svn://svn.chromium.org/blink/trunk@148354 bbb929c8-8fbe-4397-9dbb-9b2b20218538