Implement a request cache and disble retrieving a sub-region.

Implement a request cache and disble retrieving a sub-region.
SpellCheck::RequestTextChecking() adds spelling markers to a wrong place when its offset parameter is not 0. To temporarily avoid this problem, this change sends the whole text given by WebKit if SpellCheckProvider::RequestTextChecking() sends a spellcheck request. Also, this change caches the last request and its response to avoid sending unnecessary spellcheck requests.

BUG=131613
TEST=SpellCheckProviderTest.MultiLineText
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=141608

[Hajime Morrita, 2012-06-11 06:53:21]

The approach looks good. 
I added some nitpicking comments.

http://codereview.chromium.org/10533077/diff/1/chrome/renderer/spellchecker/s...
File chrome/renderer/spellchecker/spellcheck_provider.cc (right):

http://codereview.chromium.org/10533077/diff/1/chrome/renderer/spellchecker/s...
chrome/renderer/spellchecker/spellcheck_provider.cc:112: string16 request(text);
I hope this early-return-with-cache part to be a method.
Then it could be easily testable.

http://codereview.chromium.org/10533077/diff/1/chrome/renderer/spellchecker/s...
chrome/renderer/spellchecker/spellcheck_provider.cc:118:
completion->didCancelCheckingText();
This means that there should be no misspelling, right?
In that case, didFinishCheckingText() with empty result
looks making more sense even though there are no visible difference.

Same can be said to line 107.

[Hironori Bono, 2012-06-11 07:24:14]

Morita-san,

Thanks for your quick review and comments. I have added a TODO comment for your
formar comment. (For your latter comment, this change needs to cancel the
request.)

Regards,

Hironori Bono

http://codereview.chromium.org/10533077/diff/1/chrome/renderer/spellchecker/s...
File chrome/renderer/spellchecker/spellcheck_provider.cc (right):

http://codereview.chromium.org/10533077/diff/1/chrome/renderer/spellchecker/s...
chrome/renderer/spellchecker/spellcheck_provider.cc:112: string16 request(text);
Unfortunately, this code is a temporary workaround and I need deeper
investigation about the root cause of Bug 131613. That is, I will re-write this
code totally when I identified the root cause. (I have added a TODO comment
here.)

http://codereview.chromium.org/10533077/diff/1/chrome/renderer/spellchecker/s...
chrome/renderer/spellchecker/spellcheck_provider.cc:118:
completion->didCancelCheckingText();
This code means we should not change existing markers. For example, when
|last_request_| is "lasy dog" and WebKit spellchecks "lasy dog...", this code
prevents WebKit from removing the misspelled underline under "lasy". On the
other hand, if we call didFinishCheckingText with an empty result, WebKit
removes the misspelled underline under "lasy".

[Hajime Morrita, 2012-06-11 08:28:39]

got it. lgtm them.