Handle destroyed tab cases in Reader Mode

Handle destroyed tab cases in Reader Mode

There are instances where callbacks and events can be triggered
and then the host tab for Reader Mode is destroyed. This change
adds checks for these cases.

BUG=556930, 556456, 556354
Committed: https://crrev.com/727acaba3508bb21c813a43c213c7e2f5582d95d
Cr-Commit-Position: refs/heads/master@{#361168}

[mdjones, 2015-11-17 21:46:52]

mdjones@chromium.org changed reviewers:
+ wychen@chromium.org

[mdjones, 2015-11-17 21:46:53]

PTAL

[wychen, 2015-11-17 22:04:48]

lgtm

https://codereview.chromium.org/1451103004/diff/20001/chrome/android/java/src...
File
chrome/android/java/src/org/chromium/chrome/browser/dom_distiller/ReaderModeManager.java
(right):

https://codereview.chromium.org/1451103004/diff/20001/chrome/android/java/src...
chrome/android/java/src/org/chromium/chrome/browser/dom_distiller/ReaderModeManager.java:299:
private WebContentsObserver createWebContentsObserver(WebContents webContents) {
Is this only used for fallback UI for low-end devices?

[mdjones, 2015-11-17 22:43:51]

https://codereview.chromium.org/1451103004/diff/20001/chrome/android/java/src...
File
chrome/android/java/src/org/chromium/chrome/browser/dom_distiller/ReaderModeManager.java
(right):

https://codereview.chromium.org/1451103004/diff/20001/chrome/android/java/src...
chrome/android/java/src/org/chromium/chrome/browser/dom_distiller/ReaderModeManager.java:299:
private WebContentsObserver createWebContentsObserver(WebContents webContents) {
On 2015/11/17 22:04:48, wychen wrote:
> Is this only used for fallback UI for low-end devices?

No, it's still needed to refresh the distillation status when a WebContents
navigates.

[mdjones, 2015-11-17 22:45:08]

mdjones@chromium.org changed reviewers:
+ nyquist@chromium.org

[mdjones, 2015-11-17 22:45:08]

+nyquist PTAL

[nyquist, 2015-11-21 00:07:29]

lgtm

[mdjones, 2015-11-21 00:13:38]

The CQ bit was checked by mdjones@chromium.org

[commit-bot: I haz the power, 2015-11-21 00:15:38]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1451103004/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1451103004/20001

[commit-bot: I haz the power, 2015-11-21 00:19:27]

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

[commit-bot: I haz the power, 2015-11-21 00:19:28]

Try jobs failed on following builders:
  mac_chromium_compile_dbg_ng on tryserver.chromium.mac (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.mac/builders/mac_chromium_comp...)
  mac_chromium_gn_rel on tryserver.chromium.mac (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.mac/builders/mac_chromium_gn_r...)
  mac_chromium_rel_ng on tryserver.chromium.mac (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.mac/builders/mac_chromium_rel_...)

[mdjones, 2015-11-23 19:10:05]

The CQ bit was checked by mdjones@chromium.org

[mdjones, 2015-11-23 19:10:05]

The patchset sent to the CQ was uploaded after l-g-t-m from
nyquist@chromium.org, wychen@chromium.org
Link to the patchset: https://codereview.chromium.org/1451103004/#ps40001
(title: "rebase")

[commit-bot: I haz the power, 2015-11-23 19:12:09]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1451103004/40001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1451103004/40001

[commit-bot: I haz the power, 2015-11-23 20:19:40]

Committed patchset #3 (id:40001)

[commit-bot: I haz the power, 2015-11-23 20:20:30]

Patchset 3 (id:??) landed as
https://crrev.com/727acaba3508bb21c813a43c213c7e2f5582d95d
Cr-Commit-Position: refs/heads/master@{#361168}