Update context tracking to use lifecycle callbacks

[fractalwrench]

ActivityManager#getRunningTasks was deprecated on Lollipop and above. This PR changes the automatic Report context so that it is set as the name of the most recently launched Activity which is in the started state, or null if this condition cannot be met.

[coveralls]

Pull Request Test Coverage Report for Build 1047

• 12 of 13 (92.31%) changed or added relevant lines in 2 files are covered.
• 6 unchanged lines in 3 files lost coverage.
• Overall coverage increased (+0.1%) to 70.62%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
sdk/src/main/java/com/bugsnag/android/SessionTracker.java	7	8	87.5%

Files with Coverage Reduction	New Missed Lines	%
sdk/src/main/java/com/bugsnag/android/AppData.java	1	82.93%
sdk/src/main/java/com/bugsnag/android/DeviceData.java	2	74.17%
sdk/src/main/java/com/bugsnag/android/Client.java	3	51.37%

Totals
Change from base Build 1038:	0.1%
Covered Lines:	1697
Relevant Lines:	2403

---

💛 - Coveralls

[coveralls]

Pull Request Test Coverage Report for Build 1093

• 12 of 13 (92.31%) changed or added relevant lines in 2 files are covered.
• 212 unchanged lines in 7 files lost coverage.
• Overall coverage increased (+0.4%) to 70.676%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
sdk/src/main/java/com/bugsnag/android/SessionTracker.java	7	8	87.5%

Files with Coverage Reduction	New Missed Lines	%
sdk/src/main/java/com/bugsnag/android/AppData.java	1	84.09%
sdk/src/main/java/com/bugsnag/android/Breadcrumbs.java	2	93.33%
sdk/src/main/java/com/bugsnag/android/DeviceData.java	2	75.78%
sdk/src/main/java/com/bugsnag/android/Report.java	4	75.76%
sdk/src/main/java/com/bugsnag/android/Configuration.java	11	89.68%
sdk/src/main/java/com/bugsnag/android/Bugsnag.java	52	10.34%
sdk/src/main/java/com/bugsnag/android/Client.java	140	52.58%

Totals
Change from base Build 1079:	0.4%
Covered Lines:	1757
Relevant Lines:	2486

---

💛 - Coveralls

[kattrali]

Why the change here? I'd be a bit concerned as this set is accessed using a few different code paths. Even if only the key is used, all this does is derive a concurrency-safe set.

[fractalwrench]

@kattrali I've changed it to a LinkedHashSet as that retains the ordering of values. The testBasicInForeground covers the case where multiple activities launch, then one stops, and we need to access the previous activity name.

Maybe a ConcurrentLinkedDeque would be a better choice for this, if you're happy with the general approach?

[kattrali]

Yeah the approach is solid - ConcurrentLinkedDeque seems ideal for this case as well.

[fractalwrench]

Updated to use a ConcurrentLinkedDeque.

[kattrali]

Something went awry with the linter but I don't see what.

[fractalwrench]

Android Lint was failing as ConcurrentLinkedDeque is only available from API 21. I've changed the collection to use ConcurrentLinkedQueue instead, as that's been available from API 1, and we're not anticipating a large number of elements in this field.