Should not crash when background image a display:none presents on the root

Should not crash when background image a display:none presents on the root

Since my previous background refactoring CL, BoxPainter::
calculateBackgroundImageGeometry() assumes that when it is called on
the LayoutView, the root element must have a box. However the background
obscuration code in LayoutBox::computeBackgroundIsKnownToBeObscured() was
not updated at the same time. This CL corrects the early out condition
to make sure calculateBackgroundImageGeometry() is only called with a
valid box.

BUG=501560
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=197789

[trchen, 2015-06-24 01:58:54]

The CQ bit was checked by trchen@chromium.org to run a CQ dry run

[trchen, 2015-06-24 01:59:20]

trchen@chromium.org changed reviewers:
+ chrishtr@chromium.org

[trchen, 2015-06-24 01:59:21]

One-line fix for a top crasher. PTAL, thanks! :)

[commit-bot: I haz the power, 2015-06-24 01:59:22]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1200263004/1

[pdr., 2015-06-24 02:31:39]

pdr@chromium.org changed reviewers:
+ pdr@chromium.org

[pdr., 2015-06-24 02:31:40]

https://codereview.chromium.org/1200263004/diff/1/LayoutTests/fast/background...
File
LayoutTests/fast/backgrounds/root-background-display-none-no-crash-expected.txt
(right):

https://codereview.chromium.org/1200263004/diff/1/LayoutTests/fast/background...
LayoutTests/fast/backgrounds/root-background-display-none-no-crash-expected.txt:2:
html {
This doesn't seem quite right. Did you mean for this to be an -expected.html
file? Or, can you just document.write('PASS') instead of dumpAsText.

It looks like new technology is being built for these crash expectations, but
isn't quite ready yet.
https://groups.google.com/a/chromium.org/d/msg/blink-dev/MszepzweRq4/VtqGLPCK...
has more info.

[commit-bot: I haz the power, 2015-06-24 03:12:33]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-06-24 03:12:34]

Dry run: Try jobs failed on following builders:
  mac_blink_rel on tryserver.blink (JOB_FAILED,
http://build.chromium.org/p/tryserver.blink/builders/mac_blink_rel/builds/60484)

[trchen, 2015-06-24 22:03:43]

The CQ bit was checked by trchen@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2015-06-24 22:03:55]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1200263004/20001

[trchen, 2015-06-24 22:05:52]

https://codereview.chromium.org/1200263004/diff/1/LayoutTests/fast/background...
File
LayoutTests/fast/backgrounds/root-background-display-none-no-crash-expected.txt
(right):

https://codereview.chromium.org/1200263004/diff/1/LayoutTests/fast/background...
LayoutTests/fast/backgrounds/root-background-display-none-no-crash-expected.txt:2:
html {
On 2015/06/24 02:31:40, pdr wrote:
> This doesn't seem quite right. Did you mean for this to be an -expected.html
> file? Or, can you just document.write('PASS') instead of dumpAsText.
> 
> It looks like new technology is being built for these crash expectations, but
> isn't quite ready yet.
>
https://groups.google.com/a/chromium.org/d/msg/blink-dev/MszepzweRq4/VtqGLPCK...
> has more info.

Looks like dumpAsText is doing funny things when the root element has
display:none. document.write('PASS') solved the issue.

We still want dumpAsText() though, otherwise it wastes time dumping a white png.

[commit-bot: I haz the power, 2015-06-24 23:24:12]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-06-24 23:24:13]

Dry run: This issue passed the CQ dry run.

[pdr., 2015-06-25 01:11:14]

On 2015/06/24 at 23:24:13, commit-bot wrote:
> Dry run: This issue passed the CQ dry run.

LGTM

[trchen, 2015-06-25 01:18:44]

The CQ bit was checked by trchen@chromium.org

[commit-bot: I haz the power, 2015-06-25 01:19:00]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1200263004/20001

[commit-bot: I haz the power, 2015-06-25 01:22:41]

Committed patchset #2 (id:20001) as
https://src.chromium.org/viewvc/blink?view=rev&revision=197789