Improve performance in onDraw() by creating RectF object only once.

Creating RectF as member variable to save unnecessary allocation on each invocation of onDraw

When onDraw is called, everytime RectF is created which allocates new object. To compute the rect, it needs to be created only once and re-used every time when onDraw() is called altering its values, else too many RectF objects could affect performance.

This issue is found from below lint warning:
../../../tmp/tmppzTHqO/0/PopupZoomer.java:466 Avoid object allocations during draw/layout operations (preallocate and reuse instead): DrawAllocation [warning]
            RectF rect = new RectF();

Bug=None.

Committed: https://crrev.com/fc16325bd1737582a405c84f2fd7355a1a1964d2
Cr-Commit-Position: refs/heads/master@{#294349}

[wajahat, 2014-09-08 12:30:15]

wajahat.s@samsung.com changed reviewers:
+ nileshagrawal@chromium.org, yfriedman@chromium.org

[wajahat, 2014-09-08 12:30:16]

Please Review.

[Yaron, 2014-09-08 23:16:31]

On 2014/09/08 12:30:16, wajahat wrote:
> Please Review.

How did you come across this? Have you done analysis to see what other
allocations happen during onDraw and this stands out? Do you have evidence that
this is causing GCs?

[wajahat, 2014-09-09 14:28:13]

On 2014/09/08 23:16:31, Yaron wrote:
> On 2014/09/08 12:30:16, wajahat wrote:
> > Please Review.
> 
> How did you come across this? Have you done analysis to see what other
> allocations happen during onDraw and this stands out? Do you have evidence
that
> this is causing GCs?

How did you come across this? 
Wajahat: I came across this from lint warning
../../../tmp/tmppzTHqO/0/PopupZoomer.java:466 Avoid object allocations during
draw/layout operations (preallocate and reuse instead): DrawAllocation [warning]
        RectF rect = new RectF();
                     ~~~~~~~~~~~
Have you done analysis to see what other allocations happen during onDraw and
this stands out?
Wajahat: As this was the potential allocation which creates and evaluates a rect
when View onDraw is called
its better to re-use rect as member, instead of recreating locally everytime
when onDraw is called.

Do you have evidence that this is causing GCs?
Wajahat: Going by JavaPerformanceDectector
https://android.googlesource.com/platform/sdk/+/e6958586e170bb1b0bf7514a19e64...
(line 201) creating RectF once is safer

But when i checked for RectF in MAT, PopupZoomer holds 1 object for RectF

Class Name                                   | Objects | Shallow Heap
----------------------------------------------------------------------
android.graphics.RectF                       |      15 |          360
|- android.widget.ImageButton                |       3 |        1,536
|- org.chromium.content.browser.PopupZoomer  |       1 |          536
|- android.graphics.drawable.GradientDrawable|       4 |          352
|- android.view.View$AttachInfo              |       1 |          208
|- java.lang.Class                           |       1 |          152
|- android.widget.Editor$InputMethodState    |       1 |           48
----------------------------------------------------------------------
Pl. let me know your opinion in this regard. Thank you for your time.

[Yaron, 2014-09-10 01:37:16]

lgtm

https://codereview.chromium.org/549163002/diff/1/content/public/android/java/...
File
content/public/android/java/src/org/chromium/content/browser/PopupZoomer.java
(right):

https://codereview.chromium.org/549163002/diff/1/content/public/android/java/...
content/public/android/java/src/org/chromium/content/browser/PopupZoomer.java:125:
// These bounds are computed in onDraw().
perhaps update to say:
// These bounds are computed and valid for one execution of onDraw. Extracted to
a member variable to save unnecessary allocations on each invocation

(with appropriate line-breaks at 80 cols :)

[wajahat, 2014-09-10 11:34:53]

Thank you for review.
Changes have been incorporated as suggested.
PTAL!

https://codereview.chromium.org/549163002/diff/1/content/public/android/java/...
File
content/public/android/java/src/org/chromium/content/browser/PopupZoomer.java
(right):

https://codereview.chromium.org/549163002/diff/1/content/public/android/java/...
content/public/android/java/src/org/chromium/content/browser/PopupZoomer.java:125:
// These bounds are computed in onDraw().
On 2014/09/10 01:37:16, Yaron wrote:
> perhaps update to say:
> // These bounds are computed and valid for one execution of onDraw. Extracted
to
> a member variable to save unnecessary allocations on each invocation
> 
> (with appropriate line-breaks at 80 cols :)

Done.

[wajahat, 2014-09-11 06:43:47]

The CQ bit was checked by wajahat.s@samsung.com

[commit-bot: I haz the power, 2014-09-11 06:45:06]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patchset/549163002/20001

[commit-bot: I haz the power, 2014-09-11 07:43:34]

Committed patchset #2 (id:20001) as 87a9b5b342519f76b857bde7124ac06c0edd8e3a

[commit-bot: I haz the power, 2014-09-11 07:56:40]

Patchset 2 (id:??) landed as
https://crrev.com/fc16325bd1737582a405c84f2fd7355a1a1964d2
Cr-Commit-Position: refs/heads/master@{#294349}