Gather some text-input attributes and make them available for IME.

Platforms like Android need to enable/disable options like autocomplete,
autocorrect, and spellcheck outside of the control of Blink.  This change
collects those settings and includes them in the general WebTextInpuInfo.

Patch for Android side is here: https://codereview.chromium.org/422143002/

BUG=303883

Review URL: https://codereview.chromium.org/428283002

git-svn-id: svn://svn.chromium.org/blink/trunk@179478 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Use 'import' and 'imageset' request contexts where appropriate.

BUG=390497

Review URL: https://codereview.chromium.org/421723005

git-svn-id: svn://svn.chromium.org/blink/trunk@179479 bbb929c8-8fbe-4397-9dbb-9b2b20218538