Correct the default Content-Type for XHR Post with string data as per XHR specification.

Correct the default Content-Type for XHR Post with string data as per XHR specification.

As per the W3C XMLHttpRequest specification (http://www.w3.org/TR/XMLHttpRequest/#the-send%28%29-method)
the default data type for string data is "text/plain;charset=UTF-8" when content-type
is not set by the author. However "application/xml" was set as the default type.
This resulted in preflight requests being made for string data
when the content-type is not set explicitly using setRequestHeader() since "application/xml"
is not in mime-type whitelist (http://www.w3.org/TR/cors/#simple-header).

Updated the content-type as per XHR specification.
Added layout test to verify no preflight test is made when data is string in XHR POST.
Added layout test to verify "text/plain;charset=UTF-8" is set as content-type
for XHR POST with string data.
Updated the test expecations of the impacted tests.

BUG=71694
R=abarth@chromium.org, cevans@chromium.org, bbudge@chromium.org

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=155717

[ancilgeorge, 2013-08-07 16:36:50]

Requesting review.

Details on the modified test expectations:

http/tests/security/mixedContent/insecure-sync-post-xhr-allowed.html:
    https://src.chromium.org/viewvc/blink?view=revision&revision=150373 -
Consider "mixed content XHR" as mixed script instead of mixed display.

Chris, the console message in the expected.txt was printed twice before the
change, now its done once. 
If I run a similar test in the browser, the
MixedContentChecker::canDisplayInsecureContent() from where the log message is
shown
is hit once with or without the change. However in Layout test it is printed
twice without the change. Is it ok
to rebaseline this test?

As per my understanding below tests are safe to update as the main test
objective is not the content-type.
http/tests/xmlhttprequest/methods-async.html
http/tests/xmlhttprequest/methods.html:
    https://bugs.webkit.org/show_bug.cgi?id=3812 - XMLHttpRequest: PUT, DELETE,
HEAD and all other methods but POST actually do a GET.
    (https://src.chromium.org/viewvc/blink?view=revision&revision=13071)

http/tests/xmlhttprequest/methods-lower-case.html: 
    https://bugs.webkit.org/show_bug.cgi?id=8099 - XMLHttpRequest lowercase post
requests broken
    (https://src.chromium.org/viewvc/blink?view=revision&revision=13652)

http/tests/xmlhttprequest/post-content-type.html:
    https://bugs.webkit.org/show_bug.cgi?id=6197 - Add Apache HTTP server to
Layout tests
    (https://src.chromium.org/viewvc/blink?view=revision&revision=12923)

http/tests/xmlhttprequest/request-encoding2.html:
    https://bugs.webkit.org/show_bug.cgi?id=34653 - Charset parameter set by
setRequestHeader as "KOI8-R" is NOT changed to UTF-8
    (https://src.chromium.org/viewvc/blink?view=revision&revision=57544)

http/tests/xmlhttprequest/workers/methods-async.html
http/tests/xmlhttprequest/workers/methods.html:
    https://bugs.webkit.org/show_bug.cgi?id=24271 - XMLHttpRequest needs js
bindings for Workers. 
    (https://src.chromium.org/viewvc/blink?view=revision&revision=41344
    https://src.chromium.org/viewvc/blink?view=revision&revision=47467)

http/tests/xmlhttprequest/workers/shared-worker-methods-async.html
http/tests/xmlhttprequest/workers/shared-worker-methods.html:
    https://bugs.webkit.org/show_bug.cgi?id=28977
    (https://src.chromium.org/viewvc/blink?view=revision&revision=48139)

[abarth-chromium, 2013-08-07 18:14:52]

How does this new behavior compare to other browsers?

[ancilgeorge, 2013-08-07 19:26:47]

On 2013/08/07 18:14:52, abarth wrote:
> How does this new behavior compare to other browsers?

Firefox sets "text/plain;charset=UTF-8" as the default content-type for string
data.
(http://mxr.mozilla.org/mozilla-release/source/content/base/src/nsXMLHttpReque...)
Also does not make preflight request.

[abarth-chromium, 2013-08-07 19:33:01]

lgtm

Great!

[commit-bot: I haz the power, 2013-08-07 19:33:09]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/ancilgeorge@samsung.com/22601002/1

[commit-bot: I haz the power, 2013-08-07 21:31:22]

Change committed as 155717