--- a/layout/base/PresShell.cpp
+++ b/layout/base/PresShell.cpp
@@ -10861,27 +10861,33 @@ PresShell::SetupFontInflation()
   NotifyFontSizeInflationEnabledIsDirty();
 }
 
 void
 nsIPresShell::RecomputeFontSizeInflationEnabled()
 {
   mFontSizeInflationEnabledIsDirty = false;
 
+  PRES_LOG("%p: Font inflation is %s\n", this, mFontSizeInflationEnabled?"enabled":"disabled");
+  PRES_LOG("%p: Global zoom: %u\n", this, nsLayoutUtils::BrowserGlobalZoom());
+
   // When not doing global zooming, we can defer updating this bit of state
   // to the end of the calculation, if we still need to know it by then.
   if (nsLayoutUtils::BrowserGlobalZoom() != 0) {
     RecomputeDocEligibleForFontSizeInflation();
+    PRES_LOG("%p: Recompute - doc eligible: %s\n", this, mDocIsFontSizeInflationEligible?"true":"false");
     if (!mDocIsFontSizeInflationEligible) {
       mFontSizeInflationEnabled = false;
       return;
     }
   }
 
   MOZ_ASSERT(mPresContext, "our pres context should not be null");
+  PRES_LOG("%p: EmPerLine: %u\n", this, FontSizeInflationEmPerLine());
+  PRES_LOG("%p: MinTwips: %u\n", this, FontSizeInflationMinTwips());
   if ((FontSizeInflationEmPerLine() == 0 &&
       FontSizeInflationMinTwips() == 0) || mPresContext->IsChrome()) {
     mFontSizeInflationEnabled = false;
     return;
   }
 
   // Force-enabling font inflation always trumps the heuristics here.
   if (!FontSizeInflationForceEnabled()) {
@@ -10899,16 +10905,17 @@ nsIPresShell::RecomputeFontSizeInflation
         mFontSizeInflationEnabled = false;
         return;
       }
     }
   }
 
   if (nsLayoutUtils::BrowserGlobalZoom() == 0) {
     RecomputeDocEligibleForFontSizeInflation();
+    PRES_LOG("%p: Recompute - doc eligible: %s\n", this, mDocIsFontSizeInflationEligible?"true":"false");
     if (!mDocIsFontSizeInflationEligible) {
       mFontSizeInflationEnabled = false;
       return;
     }
   }
 
   mFontSizeInflationEnabled = true;
 }