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

layout/generic/nsBlockReflowContext.cpp

@@ -245,12 +245,18 @@ 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 (mWritingMode.IsOrthogonalTo(mFrame->GetWritingMode())) {
+      if (NS_UNCONSTRAINEDSIZE != aFrameRS.AvailableISize()) {
+        aFrameRS.AvailableISize() -= mBStartMargin.get() + aClearance;
+      }
+    } else {
       if (NS_UNCONSTRAINEDSIZE != aFrameRS.AvailableBSize()) {
         aFrameRS.AvailableBSize() -= mBStartMargin.get() + aClearance;
       }
     }
+  }
 
   nscoord tI = 0, tB = 0;
   // The values of x and y do not matter for floats, so don't bother