Bug 1374545 - Tests use media.memory_cache_max_size=32KB to exercise both memory&file caches - r=cpearce

This should exercise MemoryBlockCache in about 65% of tests, and FileBlockCache
in 35% of tests.

Also media.memory_caches_combined_limit_kb=256KB, to exercise the fallback to
FileBlockCache when MemoryBlockCaches are using too much memory.

MozReview-Commit-ID: A8k3espEg03

--HG--
extra : rebase_source : dd4fcbaa669912fe02098552a8a564d123f76a33

testing/profiles/prefs_general.js

@@ -45,6 +45,8 @@ user_pref("network.http.prompt-temp-redirect", false);
 user_pref("media.preload.default", 2); // default = metadata
 user_pref("media.preload.auto", 3); // auto = enough
 user_pref("media.cache_size", 1000);
+user_pref("media.memory_cache_max_size", 32);
+user_pref("media.memory_caches_combined_limit_kb", 256);
 user_pref("media.volume_scale", "0.01");
 user_pref("media.test.dumpDebugInfo", true);
 user_pref("media.dormant-on-pause-timeout-ms", 0); // Enter dormant immediately without waiting for timeout.