--- a/layout/xul/tree/nsTreeBodyFrame.cpp
+++ b/layout/xul/tree/nsTreeBodyFrame.cpp
@@ -3664,16 +3664,23 @@ nsTreeBodyFrame::PaintImage(int32_t     
   aRemainingWidth -= imageRect.width;
   if (!isRTL) {
     aCurrX += imageRect.width;
   }
 
   return result;
 }
 
+// Disable PGO for PaintText because MSVC 2015 seems to have decided
+// that it can null out the alreadyAddRefed<nsFontMetrics> used to
+// initialize fontMet after storing fontMet on the stack in the same
+// space, overwriting fontMet's stack storage with null.
+#ifdef _MSC_VER
+# pragma optimize("g", off)
+#endif
 DrawResult
 nsTreeBodyFrame::PaintText(int32_t              aRowIndex,
                            nsTreeColumn*        aColumn,
                            const nsRect&        aTextRect,
                            nsPresContext*      aPresContext,
                            nsRenderingContext& aRenderingContext,
                            const nsRect&        aDirtyRect,
                            nscoord&             aCurrX)
@@ -3796,16 +3803,19 @@ nsTreeBodyFrame::PaintText(int32_t      
                             cellContext);
 
   if (opacity != 1.0f) {
     ctx->PopGroupAndBlend();
   }
 
   return result;
 }
+#ifdef _MSC_VER
+# pragma optimize("", on)
+#endif
 
 DrawResult
 nsTreeBodyFrame::PaintCheckbox(int32_t              aRowIndex,
                                nsTreeColumn*        aColumn,
                                const nsRect&        aCheckboxRect,
                                nsPresContext*      aPresContext,
                                nsRenderingContext& aRenderingContext,
                                const nsRect&        aDirtyRect)