UI resource are evicted when LTH is set to not visible.

This change provides logic for evicting UI resources when the LTH is set to not visible (which happens when tab is backgrounded).  The resources are recovered when LTH is set to visible.

Closed. Replaced with
https://chromiumcodereview.appspot.com/23548022/

BUG=279438, 276680

[powei, 2013-08-26 23:35:38]

PTAL.  Thanks. 

Also, I checked the android side.  Looks like LTH::SetVisible(false) is never
called, so I think we're ok on that.

[ccameron, 2013-08-26 23:54:32]

This lg. It looks to me that LTHI::CanDraw() will still return true with the UI
resources having been deleted. Can you make it so that CanDraw() returns false
after UI resource eviction, until the UI resources all come back in?

https://codereview.chromium.org/23478004/diff/1/cc/trees/layer_tree_host.cc
File cc/trees/layer_tree_host.cc (right):

https://codereview.chromium.org/23478004/diff/1/cc/trees/layer_tree_host.cc#n...
cc/trees/layer_tree_host.cc:438: bool resource_lost = true;
I haven't seen this way for naming a parameter before -- someone closer to cc/
should comment on if this is okay. Might want to use an enum.

https://codereview.chromium.org/23478004/diff/1/cc/trees/layer_tree_host_impl.cc
File cc/trees/layer_tree_host_impl.cc (right):

https://codereview.chromium.org/23478004/diff/1/cc/trees/layer_tree_host_impl...
cc/trees/layer_tree_host_impl.cc:270: 
You probably need to make sure that this returns false after the UI resources
have been evicted.

[danakj, 2013-08-27 00:30:02]

https://codereview.chromium.org/23478004/diff/1/cc/trees/layer_tree_host.cc
File cc/trees/layer_tree_host.cc (right):

https://codereview.chromium.org/23478004/diff/1/cc/trees/layer_tree_host.cc#n...
cc/trees/layer_tree_host.cc:438: bool resource_lost = true;
On 2013/08/26 23:54:32, ccameron1 wrote:
> I haven't seen this way for naming a parameter before -- someone closer to cc/
> should comment on if this is okay. Might want to use an enum.

This is generally how we pass bool literals, ie we don't pass "true/false"
directly to a function without a name unless it's super obvious what it means.
An enum could work too, but maybe overkill IMO.

[powei, 2013-08-27 01:29:09]

On 2013/08/26 23:54:32, ccameron1 wrote:
> This lg. It looks to me that LTHI::CanDraw() will still return true with the
UI
> resources having been deleted. Can you make it so that CanDraw() returns false
> after UI resource eviction, until the UI resources all come back in?
> 
> https://codereview.chromium.org/23478004/diff/1/cc/trees/layer_tree_host.cc
> File cc/trees/layer_tree_host.cc (right):
> 
>
https://codereview.chromium.org/23478004/diff/1/cc/trees/layer_tree_host.cc#n...
> cc/trees/layer_tree_host.cc:438: bool resource_lost = true;
> I haven't seen this way for naming a parameter before -- someone closer to cc/
> should comment on if this is okay. Might want to use an enum.
> 
>
https://codereview.chromium.org/23478004/diff/1/cc/trees/layer_tree_host_impl.cc
> File cc/trees/layer_tree_host_impl.cc (right):
> 
>
https://codereview.chromium.org/23478004/diff/1/cc/trees/layer_tree_host_impl...
> cc/trees/layer_tree_host_impl.cc:270: 
> You probably need to make sure that this returns false after the UI resources
> have been evicted.

Added return false to CanDraw.  Please check my logic to make sure I'm not
making a bad assumption.  Thanks.

[ccameron, 2013-08-27 22:27:37]

On 2013/08/27 01:29:09, powei wrote:
> On 2013/08/26 23:54:32, ccameron1 wrote:
> > This lg. It looks to me that LTHI::CanDraw() will still return true with the
> UI
> > resources having been deleted. Can you make it so that CanDraw() returns
false
> > after UI resource eviction, until the UI resources all come back in?
> > 
> > https://codereview.chromium.org/23478004/diff/1/cc/trees/layer_tree_host.cc
> > File cc/trees/layer_tree_host.cc (right):
> > 
> >
>
https://codereview.chromium.org/23478004/diff/1/cc/trees/layer_tree_host.cc#n...
> > cc/trees/layer_tree_host.cc:438: bool resource_lost = true;
> > I haven't seen this way for naming a parameter before -- someone closer to
cc/
> > should comment on if this is okay. Might want to use an enum.
> > 
> >
>
https://codereview.chromium.org/23478004/diff/1/cc/trees/layer_tree_host_impl.cc
> > File cc/trees/layer_tree_host_impl.cc (right):
> > 
> >
>
https://codereview.chromium.org/23478004/diff/1/cc/trees/layer_tree_host_impl...
> > cc/trees/layer_tree_host_impl.cc:270: 
> > You probably need to make sure that this returns false after the UI
resources
> > have been evicted.
> 
> Added return false to CanDraw.  Please check my logic to make sure I'm not
> making a bad assumption.  Thanks.

I think there's still an issue with this ... we had to do something similar for
resource eviction, and it was very subtle.

Maybe we should sit down together on this (but first I'm going to have to study
this a bit).