Bug 1284651. Allow the image surface cache to grow beyond 1GB on 64bit builds with sufficient memory. r=aosmond

Before this patch: surface cache size = min(1GB, system_memory/4)
After this patch: surface cache size = min(32bit ? 1GB : 2GB , system_memory/4)

sizeof(uintptr_t) is the best I can figure out to detect 32bit builds.

Differential Revision: https://phabricator.services.mozilla.com/D45092

--HG--
extra : moz-landing-system : lando

Author: tnikkel

image/SurfaceCache.cpp

@@ -1391,6 +1391,11 @@ void SurfaceCache::Initialize() {
   uint64_t surfaceCacheMaxSizeKB =
       StaticPrefs::image_mem_surfacecache_max_size_kb_AtStartup();
 
+  if (sizeof(uintptr_t) <= 4) {
+    // Limit surface cache to 1 GB if our address space is 32 bit.
+    surfaceCacheMaxSizeKB = 1024 * 1024;
+  }
+
   // A knob determining the actual size of the surface cache. Currently the
   // cache is (size of main memory) / (surface cache size factor) KB
   // or (surface cache max size) KB, whichever is smaller. The formula

modules/libpref/init/StaticPrefList.yaml

@@ -3750,7 +3750,7 @@
 # Maximum size for the surface cache, in kilobytes.
 - name: image.mem.surfacecache.max_size_kb
   type: uint32_t
-  value: 1024 * 1024
+  value: 2024 * 1024
   mirror: once
 
 # Minimum timeout for expiring unused images from the surface cache, in