Bug 1441308 - Add pref to disable texture cache clear r=bholley

To facilitate testing of document splitting before it is preffed on,
I'm adding a pref to disable clearing the texture cache, since this
will currently crash the browser with doc splitting on.

Depends on D13840

Differential Revision: https://phabricator.services.mozilla.com/D13841

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

gfx/thebes/gfxPlatform.cpp

@@ -579,6 +579,7 @@ void WebRenderDebugPrefChangeCallback(const char* aPrefName, void*) {
   GFX_WEBRENDER_DEBUG(".gpu-cache", 1 << 12)
   GFX_WEBRENDER_DEBUG(".slow-frame-indicator", 1 << 13)
   GFX_WEBRENDER_DEBUG(".texture-cache.clear-evicted", 1 << 14)
+  GFX_WEBRENDER_DEBUG(".texture-cache.disable-shrink", 1 << 16)
 #undef GFX_WEBRENDER_DEBUG
 
   gfx::gfxVars::SetWebRenderDebugFlags(flags);

gfx/wr/webrender/src/texture_cache.rs

@@ -555,6 +555,13 @@ impl TextureCache {
     /// Clear all standalone textures in the cache.
     pub fn clear_standalone(&mut self) {
         debug_assert!(!self.now.is_valid());
+        // This pref just helps us avoid crashes when we begin using multiple documents.
+        // What we need to do for clear to work correctly with multiple documents is
+        // to ensure that we generate frames for all documents whenever we do this.
+        if self.debug_flags.contains(DebugFlags::TEXTURE_CACHE_DBG_DISABLE_SHRINK) {
+            return;
+        }
+
         let mut per_doc_data = mem::replace(&mut self.per_doc_data, FastHashMap::default());
         for (&_, doc_data) in per_doc_data.iter_mut() {
             let standalone_entry_handles = mem::replace(
@@ -573,6 +580,13 @@ impl TextureCache {
 
     /// Clear all shared textures in the cache.
     pub fn clear_shared(&mut self) {
+        // This pref just helps us avoid crashes when we begin using multiple documents.
+        // What we need to do for clear to work correctly with multiple documents is
+        // to ensure that we generate frames for all documents whenever we do this.
+        if self.debug_flags.contains(DebugFlags::TEXTURE_CACHE_DBG_DISABLE_SHRINK) {
+            return;
+        }
+
         self.unset_doc_data();
         let mut per_doc_data = mem::replace(&mut self.per_doc_data, FastHashMap::default());
         for (&_, doc_data) in per_doc_data.iter_mut() {

gfx/wr/webrender_api/src/api.rs

@@ -990,6 +990,7 @@ bitflags! {
         const TEXTURE_CACHE_DBG_CLEAR_EVICTED = 1 << 14;
         /// Show picture caching debug overlay
         const PICTURE_CACHING_DBG   = 1 << 15;
+        const TEXTURE_CACHE_DBG_DISABLE_SHRINK = 1 << 16;
     }
 }
 

modules/libpref/init/all.js

@@ -941,6 +941,7 @@ pref("gfx.webrender.blob.paint-flashing", false);
 // WebRender debugging utilities.
 pref("gfx.webrender.debug.texture-cache", false);
 pref("gfx.webrender.debug.texture-cache.clear-evicted", true);
+pref("gfx.webrender.debug.texture-cache.disable-shrink", false);
 pref("gfx.webrender.debug.render-targets", false);
 pref("gfx.webrender.debug.gpu-cache", false);
 pref("gfx.webrender.debug.alpha-primitives", false);