Fix combobox alignment issue on views.

This CL lines up the text in both text fields and drop down inputs in the
autofill dialog (a.k.a requestAutocomplete()).

BUG=302076
TEST=textbox and combobox text aligns vertically (see bug for example)
R=estade@chromium.org

Review URL: https://codereview.chromium.org/26053002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@227475 0039d316-1c4b-4281-b951-d872f2087c98
Add ComboboxModel::IsItemEnabledAt

This CL enables to switch the enabling/disabling state of menu item of a Combobox.

Concretely, this feature is needed by new Translate UI. Actually, the Translate current infobar has this feature. For example, the Translate UI has the source language and the target language selectors as Comboboxes, and when English is selected as the source language, English in the target language selector should be disabled.

BUG=276181

Review URL: https://codereview.chromium.org/26219002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@227476 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 227476
Refactored loading of applications / extensions icons.
Added ImageLoader::LoadExtensionIconAsync() and ImageLoader::LoadExtensionIconDataURLAsync().
Moved all apps / extension loading code to ImageLoader.

BUG=297298, 297301, 304180

Review URL: https://codereview.chromium.org/26161002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@227477 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 227477