Trim whitespace that comes right before a <br> when trimming whitespace. Bug

132561 relanding, r+sr=dbaron

layout/generic/nsLineLayout.cpp

@@ -1006,7 +1006,7 @@ nsLineLayout::ReflowFrame(nsIFrame* aFrame,
   // the float.
   if (frameType) {
     if (nsLayoutAtoms::placeholderFrame == frameType) {
-      pfd->SetFlag(PFD_ISPLACEHOLDERFRAME, PR_TRUE);
+      pfd->SetFlag(PFD_SKIPWHENTRIMMINGWHITESPACE, PR_TRUE);
       nsIFrame* outOfFlowFrame = nsLayoutUtils::GetFloatFromPlaceholder(aFrame);
       if (outOfFlowFrame) {
         nsPlaceholderFrame* placeholder = NS_STATIC_CAST(nsPlaceholderFrame*, aFrame);
@@ -1062,6 +1062,9 @@ nsLineLayout::ReflowFrame(nsIFrame* aFrame,
     else if (nsLayoutAtoms::letterFrame==frameType) {
       pfd->SetFlag(PFD_ISLETTERFRAME, PR_TRUE);
     }
+    else if (nsLayoutAtoms::brFrame == frameType) {
+      pfd->SetFlag(PFD_SKIPWHENTRIMMINGWHITESPACE, PR_TRUE);
+    }
   }
 
   mSpaceManager->Translate(-tx, -ty);
@@ -2617,7 +2620,7 @@ nsLineLayout::TrimTrailingWhiteSpaceIn(PerSpanData* psd,
       }
     }
     else if (!pfd->GetFlag(PFD_ISTEXTFRAME) &&
-             !pfd->GetFlag(PFD_ISPLACEHOLDERFRAME)) {
+             !pfd->GetFlag(PFD_SKIPWHENTRIMMINGWHITESPACE)) {
       // If we hit a frame on the end that's not text and not a placeholder,
       // then there is no trailing whitespace to trim. Stop the search.
       *aDeltaWidth = 0;

layout/generic/nsLineLayout.h

@@ -397,14 +397,15 @@ protected:
 #define PFD_ISLETTERFRAME               0x00000010
 #define PFD_ISSTICKY                    0x00000020
 #define PFD_ISBULLET                    0x00000040
-#define PFD_ISPLACEHOLDERFRAME          0x00000080
-#define PFD_LASTFLAG                    PFD_ISPLACEHOLDERFRAME
+#define PFD_SKIPWHENTRIMMINGWHITESPACE  0x00000080
+#define PFD_LASTFLAG                    PFD_SKIPWHENTRIMMINGWHITESPACE
 
-    PRPackedBool mFlags;
+    PRUint8 mFlags;
 
     void SetFlag(PRUint32 aFlag, PRBool aValue)
     {
       NS_ASSERTION(aFlag<=PFD_LASTFLAG, "bad flag");
+      NS_ASSERTION(aFlag<=PR_UINT8_MAX, "bad flag");
       NS_ASSERTION(aValue==PR_FALSE || aValue==PR_TRUE, "bad value");
       if (aValue) { // set flag
         mFlags |= aFlag;