Disable proguard optimization that removes write-only fields.

Disable proguard optimization that removes write-only fields.

Static fields in Java are often assumed to stay alive throughout the
runtime of the entire program. However, the proguard
field/removal/writeonly optimization removes even static fields that are
only written to. This breaks some WebView code that relies on static
fields to hold onto a file-lock which prevents file-access from other
processes.

.dex size increase after this change:
uncompressed dex, Chrome    5670532 -> 5714496, diff 43964
compressed dex, Chrome      2491927 -> 2512376, diff 20449
uncompressed dex, WebView    999208 -> 1005192, diff  5984
compressed dex, WebView      430871 ->  434089, diff  3218

BUG=647291

[gsennton, 2016-11-09 18:55:36]

gsennton@chromium.org changed reviewers:
+ torne@chromium.org

[gsennton, 2016-11-09 18:56:11]

I added classes.dex measurements to the bug rather than here.

[agrieve, 2016-11-09 20:38:24]

On 2016/11/09 18:56:11, gsennton wrote:
> I added classes.dex measurements to the bug rather than here.

40kb would be sad to lose. Would it make sense to use JNI to hold onto such
references instead?

[gsennton, 2016-11-10 10:23:41]

On 2016/11/09 20:38:24, agrieve wrote:
> On 2016/11/09 18:56:11, gsennton wrote:
> > I added classes.dex measurements to the bug rather than here.
> 
> 40kb would be sad to lose. Would it make sense to use JNI to hold onto such
> references instead?

I guess that would solve the problem in our case - but on the other hand it is
very non-intuitive that a static variable (even if write-only) becomes garbage
collected at any point during code execution.
IMO if we want to keep the field/removal/write-only optimization we should have
some kind of warning/error notifying developers if they add static write-only
variables since these will behave in a non-intuitive way.

[Torne, 2016-11-10 13:42:02]

Yeah, that's too big a size regression, we'll try -keep'ing the field instead as
that should probably work, and if not come up with another way to retain the
reference.

[gsennton, 2016-11-11 13:11:10]

Description was changed from

==========
Disable proguard optimization that removes write-only fields.

Static fields in Java are often assumed to stay alive throughout the
runtime of the entire program. However, the proguard
field/removal/writeonly optimization removes even static fields that are
only written to. This breaks some WebView code that relies on static
fields to hold onto a file-lock which prevents file-access from other
processes.

.dex size increase after this change:
uncompressed dex, Chrome    5670532 -> 5714496, diff 43964
compressed dex, Chrome      2491927 -> 2512376, diff 20449
uncompressed dex, WebView    999208 -> 1005192, diff  5984
compressed dex, WebView      430871 ->  434089, diff  3218

BUG=647291
==========

to

==========
Disable proguard optimization that removes write-only fields.

Static fields in Java are often assumed to stay alive throughout the
runtime of the entire program. However, the proguard
field/removal/writeonly optimization removes even static fields that are
only written to. This breaks some WebView code that relies on static
fields to hold onto a file-lock which prevents file-access from other
processes.

.dex size increase after this change:
uncompressed dex, Chrome    5670532 -> 5714496, diff 43964
compressed dex, Chrome      2491927 -> 2512376, diff 20449
uncompressed dex, WebView    999208 -> 1005192, diff  5984
compressed dex, WebView      430871 ->  434089, diff  3218

BUG=647291
==========

[gsennton, 2016-11-11 13:14:57]

On 2016/11/10 13:42:02, Torne wrote:
> Yeah, that's too big a size regression, we'll try -keep'ing the field instead
as
> that should probably work, and if not come up with another way to retain the
> reference.

Closing this CL given Torne's last comment.