Version 3.3.1 - native improvements

[konraddysput]

Backtrace-Unity 3.3.1 update

This patch adjusts the approach Backtrace-unity uses to detect low memory situations. Previously Backtrace report low memory warning to Backtrace when the lowMemoryWarning callback occurred. This updated approach allows the system to detect out-of-memory crashes via a native OS library and adjustments to the data collected by Backtrace.

On iOS - The system reports the out-of-memory exception when the lowMemoryWarning occurred and when the application unexpectedly exits. On the next application startup, Backtrace will analyze the status file. If the status file is available and the following conditions are met, then the Backtrace-Unity integration sends an OutOfMemory exception to Backtrace. The conditions that are checked are:

• application version is the same,
• system version is the same,
• debugger wasn't connected on the last session,
• out of memory warning occurred,
• out of memory resource is available

On Android - The report generated was extended with attributes to let developers know the following information:

• memory warning occurred,
• last time when memory warning occurred

Testing strategy

1. Integration/Unit tests

• make sure all of them are passing

2. Manual tests

• on Android (oom enabled)
  Run the application that generates a lot of textures to see how the application performs with out of memory exception and try to generate crash with attributes

• on iOS (oom enabled)
  validate if the status file is generated on application startup with basic information about the application
  validate if the status file has application version, systemVersion, debug information on the application startup,
  validate if application stores low memory warning when the lowMemoryWarning event occurred,
  validate if application stores report attributes when the lowMemoryWarning event occurred,
  validate if application upload the out of memory report when application version, systemVersion, debugging information are the same,
  validate if the application doesn't upload the out of memory report when application version, systemVersion, debugging information are the same,

• on iOS (oom disabled)
  check if status json file is generated,
  check if notification are generated when lowMemoryWarning or other events happening.

[rqbacktrace]

Looks good, just found some spacing issues

[jasoncdavis0]

Updated the change log and description of PR.