Bug 1144501 - Take account of orthogonal writing modes when adjusting available size to reflow a child frame. r=smontagu

layout/generic/nsBlockReflowContext.cpp

@@ -245,10 +245,16 @@ nsBlockReflowContext::ReflowBlock(const LogicalRect&  aSpace,
     printf(" margin => %d, clearance => %d\n", mBStartMargin.get(), aClearance);
 #endif
 
-    // Adjust the available block size if it's constrained so that the
+    // Adjust the available size if it's constrained so that the
     // child frame doesn't think it can reflow into its margin area.
-    if (NS_UNCONSTRAINEDSIZE != aFrameRS.AvailableBSize()) {
+    if (mWritingMode.IsOrthogonalTo(mFrame->GetWritingMode())) {
-      aFrameRS.AvailableBSize() -= mBStartMargin.get() + aClearance;
+      if (NS_UNCONSTRAINEDSIZE != aFrameRS.AvailableISize()) {
+        aFrameRS.AvailableISize() -= mBStartMargin.get() + aClearance;
+      }
+    } else {
+      if (NS_UNCONSTRAINEDSIZE != aFrameRS.AvailableBSize()) {
+        aFrameRS.AvailableBSize() -= mBStartMargin.get() + aClearance;
+      }
     }
   }