Revert 151419 - Replace HistoryQuickProvider protobuf-based caching with an SQLite-based database.

Revert 151419 - Replace HistoryQuickProvider protobuf-based caching with an SQLite-based database.

The protobuf-based cache was only being read at startup and written at shutdown. (Except that when the cache could not be read at startup the cache would immediately be saved upon private data reconstruction from the History database.) With the new implementation using an SQLite database for the HQP cache the private data will be restored from the cache database at startup and continually updated during normal operation. There is no need to flush or write the cache at shutdown as it is constantly kept up-to-date.

Detailed comments about the changes made in this CL can be found in the document shared separately.

Reviewer suggestions:
  sky: for proper thread usage. Also chrome/browser/ui/ and chrome/browser/visitedlink/.
  pkasting: for whatever you'd like to check over but please look over the design document shared separately.
  shess: please take a look at database usage in chrome/browser/history/in_memory_url_cache_database.h/.cc.

BUG=95686, 95876, 131668
TEST=New tests added, old tests updated, all tests pass.
To manually verify changes:
NOTE: For tests using chrome://omnibox be sure to check the "Show results per provider" and then look at the results for the HistoryQuickProvider.
1) New visits: Type an URL never visited before. Bring up new tab. Start typing the URL or parts of the page title or both and verify that the page is offered as a suggestion.
2) New visits: Type an URL never visited before. Do search using chrome://omnibox. New visit should show.
3) Delete visit: Visit some pages and verify they have been recorded. Bring up history and delete one of the visits. Check via chrome://omnibox that it was deleted.
4) Clear history: Visit some pages. Clear the visit history. Check via chrome://omnibox that none of the visits are still returned by the HQP.
5) Updated site: Create a local page and visit it. Search using chrome://omnibox by page title and verify it can be found. Change the page title dramatically and revisit the page. Verify via chrome://oomnibox that the page can be found by words from the new title.
Review URL: https://chromiumcodereview.appspot.com/10477018

TBR=mrossetti@chromium.org
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=151424

[mrossetti, 2012-08-14 14:47:25]

LGTM