WebKit2 shouldn't try to send an empty user agent. In WebKit2/WebProcess/WebPage/WebPage.cpp, when we are returning the user agent, we return the custom one if it is not null, however, this should be if it is not empty, because we don't want to return an empty string for the user agent.
Created attachment 71981 [details]
(In reply to comment #1)
> Created an attachment (id=71981) [details]
> [PATCH] Fix
Will send out a new patch with a better explanation and a test.
Created attachment 71986 [details]
[PATCH] Fix with test
Attachment 71986 [details] did not pass style-queue:
Failed to run "['WebKitTools/Scripts/check-webkit-style']" exit_code: 1
WebKitTools/TestWebKitAPI/Tests/WebKit2/PreventEmptyUserAgent.cpp:26: Found other header before WebCore config.h. Should be: config.h, primary header, blank line, and then alphabetically sorted. [build/include_order] 
WebKitTools/TestWebKitAPI/Tests/WebKit2/PreventEmptyUserAgent.cpp:28: Alphabetical sorting problem. [build/include_order] 
Total errors found: 2 in 6 files
If any of these errors are false positives, please file a bug against check-webkit-style.
Landed in r70658.
http://trac.webkit.org/changeset/70658 might have broken GTK Linux 32-bit Debug
http://trac.webkit.org/changeset/70659 might have broken GTK Linux 32-bit Debug