Add LowMemoryNotification to the API on Android platform....

Add LowMemoryNotification to the API on Android platform.

Android system provides a unique feature that it sends a notification to the browser in low memory condition, and the browser cleans up cache and frees resources. Forcing a GC in low memory condition can free DOM objects and also can shrink the old spaces.

[Mads Ager (chromium), 2009-08-19 17:24:23]

LGTM once these comments have been addressed.

http://codereview.chromium.org/173016/diff/1/2
File include/v8.h (right):

http://codereview.chromium.org/173016/diff/1/2#newcode2246
Line 2246: #if defined(ANDROID)
I don't think we need to hide this under #if defined(ANDROID). I think the
method makes sense on other platforms as well.

It should be entirely up to V8 what to do when we get this notification, so the
documentation should be more abstract.  Something along the lines of:

"Optional notification that the system is running low on memory.  V8 uses these
notifications to attempt to free memory."

Then the implementation can contain the #if defined(ANDROID) and do a full GC on
the Android platform and do nothing on the other platforms for now.

http://codereview.chromium.org/173016/diff/1/4
File src/heap.cc (right):

http://codereview.chromium.org/173016/diff/1/4#newcode322
Line 322: bool saved_always_compact_flag = FLAG_always_compact;
I would prefer to not use the flags to signal that a compacting collection is
requested.

http://codereview.chromium.org/173016/diff/1/5
File src/heap.h (right):

http://codereview.chromium.org/173016/diff/1/5#newcode629
Line 629: // Performs a full garbage collection. Force compaction if the second
if the second parameter -> if the parameter

[Feng Qian, 2009-08-20 00:06:08]

Replaced by
http://codereview.chromium.org/173102

which add a global flag to MarkCompactCollector for forcing compaction.

http://codereview.chromium.org/173016/diff/1/2
File include/v8.h (right):

http://codereview.chromium.org/173016/diff/1/2#newcode2246
Line 2246: #if defined(ANDROID)
On 2009/08/19 17:24:23, Mads Ager wrote:
> I don't think we need to hide this under #if defined(ANDROID). I think the
> method makes sense on other platforms as well.
> 
> It should be entirely up to V8 what to do when we get this notification, so
the
> documentation should be more abstract.  Something along the lines of:
> 
> "Optional notification that the system is running low on memory.  V8 uses
these
> notifications to attempt to free memory."
> 
> Then the implementation can contain the #if defined(ANDROID) and do a full GC
on
> the Android platform and do nothing on the other platforms for now.

Done.

http://codereview.chromium.org/173016/diff/1/4
File src/heap.cc (right):

http://codereview.chromium.org/173016/diff/1/4#newcode322
Line 322: bool saved_always_compact_flag = FLAG_always_compact;
I had the same thought. There is no obvious way to do it now, how about a TODO
here?

On 2009/08/19 17:24:23, Mads Ager wrote:
> I would prefer to not use the flags to signal that a compacting collection is
> requested.

[Kasper Lund, 2009-08-20 06:54:56]

http://codereview.chromium.org/173016/diff/1/3
File src/api.cc (right):

http://codereview.chromium.org/173016/diff/1/3#newcode2611
Line 2611: #endif
Would it make sense to always do a Heap::UncommitFromSpace here - on all
platforms?