Bug 1106827 - Improve handling of Android memory pressure events r=rnewman

mobile/android/base/MemoryMonitor.java

@@ -94,18 +94,33 @@ class MemoryMonitor extends BroadcastReceiver {
             return;
         }
 
-        if (level >= ComponentCallbacks2.TRIM_MEMORY_COMPLETE) {
-            increaseMemoryPressure(MEMORY_PRESSURE_HIGH);
-        } else if (level >= ComponentCallbacks2.TRIM_MEMORY_MODERATE) {
-            increaseMemoryPressure(MEMORY_PRESSURE_MEDIUM);
-        } else if (level >= ComponentCallbacks2.TRIM_MEMORY_UI_HIDDEN) {
-            // includes TRIM_MEMORY_BACKGROUND
-            increaseMemoryPressure(MEMORY_PRESSURE_CLEANUP);
-        } else {
-            // levels down here mean gecko is the foreground process so we
-            // should be less aggressive with wiping memory as it may impact
-            // user experience.
-            increaseMemoryPressure(MEMORY_PRESSURE_LOW);
+        if (level == ComponentCallbacks2.TRIM_MEMORY_COMPLETE) {
+            // We seem to get this just by entering the task switcher or hitting the home button.
+            // Seems bogus, because we are the foreground app, or at least not at the end of the LRU list.
+            // Just ignore it, and if there is a real memory pressure event (CRITICAL, MODERATE, etc),
+            // we'll respond appropriately.
+            return;
+        }
+
+        switch (level) {
+            case ComponentCallbacks2.TRIM_MEMORY_RUNNING_CRITICAL:
+            case ComponentCallbacks2.TRIM_MEMORY_MODERATE:
+                // TRIM_MEMORY_MODERATE is the highest level we'll respond to while backgrounded
+                increaseMemoryPressure(MEMORY_PRESSURE_HIGH);
+                break;
+            case ComponentCallbacks2.TRIM_MEMORY_RUNNING_MODERATE:
+                increaseMemoryPressure(MEMORY_PRESSURE_MEDIUM);
+                break;
+            case ComponentCallbacks2.TRIM_MEMORY_RUNNING_LOW:
+                increaseMemoryPressure(MEMORY_PRESSURE_LOW);
+                break;
+            case ComponentCallbacks2.TRIM_MEMORY_UI_HIDDEN:
+            case ComponentCallbacks2.TRIM_MEMORY_BACKGROUND:
+                increaseMemoryPressure(MEMORY_PRESSURE_CLEANUP);
+                break;
+            default:
+                Log.d(LOGTAG, "Unhandled onTrimMemory() level " + level);
+                break;
         }
     }
 
@@ -140,6 +155,8 @@ class MemoryMonitor extends BroadcastReceiver {
             mMemoryPressure = level;
         }
 
+        Log.d(LOGTAG, "increasing memory pressure to " + level);
+
         // since we don't get notifications for when memory pressure is off,
         // we schedule our own timer to slowly back off the memory pressure level.
         // note that this will reset the time to next decrement if the decrementer