Bug 1550504 - Add pref to allow slow frames logging, disabled by default. r=jrmuizel

Differential Revision: https://phabricator.services.mozilla.com/D30508

gfx/thebes/gfxPlatform.cpp

@@ -3167,6 +3167,10 @@ class FrameStatsComparator {
 };
 
 void gfxPlatform::NotifyFrameStats(nsTArray<FrameStats>&& aFrameStats) {
+  if (!gfxPrefs::LoggingSlowFramesEnabled()) {
+    return;
+  }
+
   FrameStatsComparator comp;
   for (FrameStats& f : aFrameStats) {
     mFrameStats.InsertElementSorted(f, comp);

gfx/thebes/gfxPrefs.h

@@ -507,6 +507,7 @@ class gfxPrefs final {
   // The maximums here are quite conservative, we can tighten them if problems show up.
   DECL_GFX_PREF(Once, "gfx.logging.texture-usage.enabled",     GfxLoggingTextureUsageEnabled, bool, false);
   DECL_GFX_PREF(Once, "gfx.logging.peak-texture-usage.enabled",GfxLoggingPeakTextureUsageEnabled, bool, false);
+  DECL_GFX_PREF(Once, "gfx.logging.slow-frames.enabled",       LoggingSlowFramesEnabled, bool, false);
   // Use gfxPlatform::MaxAllocSize instead of the pref directly
   DECL_GFX_PREF(Once, "gfx.max-alloc-size",                    MaxAllocSizeDoNotUseDirectly, int32_t, (int32_t)500000000);
   // Use gfxPlatform::MaxTextureSize instead of the pref directly

modules/libpref/init/all.js

@@ -884,6 +884,7 @@ pref("gfx.draw-color-bars", false);
 pref("gfx.logging.painted-pixel-count.enabled", false);
 pref("gfx.logging.texture-usage.enabled", false);
 pref("gfx.logging.peak-texture-usage.enabled", false);
+pref("gfx.logging.slow-frames.enabled", false);
 
 pref("gfx.ycbcr.accurate-conversion", false);