Patch for Chromium settings crash

[John Carr]

If I select "Settings" then "Exit" from the menu at top right,
chrome crashes every time.  Same with "History" instead of "Settings".

I am running FreeBSD 10.0 on amd64, chromium package 32.0.1700.107.

I started X with xinit, basically just starting a few xterms.  Maybe
some service that chrome assumes is always running isn't running.
I assume this crash would have been noticed if it affected a standard
desktop environment.

I attached a patch, plus a second patch to make the build work in debug
mode so I could find the problem.

I'm sending this to the FreeBSD address because I can't tell if the
bug is in a porting change or the original code.

The debug build failure may be caused by a clang bug.  An inline
function is not being found at final link.  I made it not inline.

The stack trace below may explain the crash better than I can.
Note the null "this" pointer.

When the browser shuts down it calls a bunch of destructors.
The MediaGalleriesHandler destructor calls media_file_system_registry(),
There is no media file system registry, so it creates one.
The new MediaFileSystemRegistry tries to hook itself onto the global
StorageMonitor(), which has already been destroyed.

I don't understand the media gallery code, so I just added a test for
null pointer near the point of the crash.

(gdb) bt
#0  StorageMonitor::AddObserver (this=0x0, obs=0x81a335e50)
    at ref_counted.h:260
#1  0x0000000000a058b6 in MediaFileSystemRegistry (this=0x81a335e50)
    at ../../chrome/browser/media_galleries/media_file_system_registry.cc:594
#2  0x00000000009c7e1b in BrowserProcessImpl::media_file_system_registry (
    this=0x81380d000) at ../../chrome/browser/browser_process_impl.cc:657
#3  0x0000000002d8c5fa in ~MediaGalleriesHandler (this=0x81a254040)
    at ../../chrome/browser/ui/webui/options/media_galleries_handler.cc:34
#4  0x0000000002d8c4ee in ~MediaGalleriesHandler (this=0x81a254040)
    at ../../chrome/browser/ui/webui/options/media_galleries_handler.cc:28
#5  0x0000000002f35e02 in ~ScopedVector (this=0x8165ae470) at stl_util.h:44
#6  0x0000000002f34528 in ~WebUIImpl (this=0x8165ae420) at scoped_vector.h:36
#7  0x0000000002f3448e in ~WebUIImpl (this=0x8165ae420)
    at ../../content/browser/webui/web_ui_impl.cc:53
#8  0x0000000002cf4cdf in ~UberUI (this=0x81a03a130) at stl_util.h:152
#9  0x0000000002cf4c8e in ~UberUI (this=0x81a03a130)
    at ../../chrome/browser/ui/webui/uber/uber_ui.cc:140
#10 0x0000000002f3450b in ~WebUIImpl (this=0x8165aeb00) at scoped_ptr.h:137
#11 0x0000000002f3448e in ~WebUIImpl (this=0x8165aeb00)
    at ../../content/browser/webui/web_ui_impl.cc:53
#12 0x0000000002f1aa64 in ~WebContentsImpl (this=<value optimized out>)
    at ../../content/browser/web_contents/web_contents_impl.cc:429
#13 0x0000000002f1a35e in ~WebContentsImpl (this=0x8139d8200)

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