[Cocoa] Purge SQLite page cache when under memory pressure.

<https://webkit.org/b/142139>
<rdar://problem/19997739>

Reviewed by Pratik Solanki.

Call out to sqlite3 cache purging SPI on Cocoa platforms when
we need to free up some extra memory.

* platform/cocoa/MemoryPressureHandlerCocoa.mm:
(WebCore::MemoryPressureHandler::platformReleaseMemory):


Canonical link: https://commits.webkit.org/160195@main
git-svn-id: https://svn.webkit.org/repository/webkit/trunk@180847 268f45cc-cd09-0410-ab3c-d52691b4dbfc

Source/WebCore/ChangeLog

@@ -1,3 +1,17 @@
+2015-02-28  Andreas Kling  <akling@apple.com>
+
+        [Cocoa] Purge SQLite page cache when under memory pressure.
+        <https://webkit.org/b/142139>
+        <rdar://problem/19997739>
+
+        Reviewed by Pratik Solanki.
+
+        Call out to sqlite3 cache purging SPI on Cocoa platforms when
+        we need to free up some extra memory.
+
+        * platform/cocoa/MemoryPressureHandlerCocoa.mm:
+        (WebCore::MemoryPressureHandler::platformReleaseMemory):
+
 2015-02-28  Simon Fraser  <simon.fraser@apple.com>
 
         FrameView::layoutTimerFired() should update style if needed before doing layout

Source/WebCore/platform/cocoa/MemoryPressureHandlerCocoa.mm

@@ -45,11 +45,17 @@
 #endif
 
 extern "C" void cache_simulate_memory_warning_event(uint64_t);
+extern "C" void _sqlite3_purgeEligiblePagerCacheMemory(void);
 
 namespace WebCore {
 
 void MemoryPressureHandler::platformReleaseMemory(bool critical)
 {
+    {
+        ReliefLogger log("Purging SQLite caches");
+        _sqlite3_purgeEligiblePagerCacheMemory();
+    }
+
     {
         ReliefLogger log("Drain LayerPools");
         for (auto& pool : LayerPool::allLayerPools())