Fix issue that IME can't be enabled when set Plugin mode to "Click to play".

In normal mode, the plugin is created at the moment the page is loaded. Then when the first time the plugin is clicked. It will set the flag "has_webkit_focus_" true in real plugin instance. Then, send out the focus change notification in PepperPluginInstanceImpl::SetWebKitFocus, which will finally affect the IME stuff.

However, at "Click to play" mode, WebViewPlugin is created at first, which will be replaced by real plugin. When the first time we click, the real plugin is created, loaded. But no focus is set in real plugin, which cause the IME stuff can't be enabled. 

In solution, we transfer the |focused_| in WebViewPlugin to new plugin after it loaded.

BUG=336740

Review URL: https://codereview.chromium.org/144803003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@251303 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 251303
Move TranslatePrefs to the Translate component

TranslatePrefs now needs the path to preferences in its constructor.
To help with this, a helper method is added to TranslateTabHelper to build
TranslatePrefs instances.
As a result, TranslatePrefs are no longer instantiated on the stack, but rather
on the heap.

BUG=335079
TBR=battre, jochen, joi

Review URL: https://codereview.chromium.org/159883002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@251305 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 251305
Fix (or tag) uses of explicit '64' instead of GL_MAILBOX_SIZE_CHROMIUM

That way we can easily change the size later. Security says 64 may be overkill.

BUG=None

Review URL: https://codereview.chromium.org/138763009

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@251306 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 251306