Fix bug with optimized try-catch on ARM/MIPS.

runtime/vm/flow_graph_allocator.cc

Index: runtime/vm/flow_graph_allocator.cc
===================================================================
--- runtime/vm/flow_graph_allocator.cc	(revision 25871)
+++ runtime/vm/flow_graph_allocator.cc	(working copy)
@@ -60,12 +60,6 @@
 }
 
 
-static intptr_t NextInstructionPos(intptr_t pos) {
-  ASSERT(IsInstructionStartPosition(pos));
-  return pos + 2;
-}
-
-
 FlowGraphAllocator::FlowGraphAllocator(const FlowGraph& flow_graph)
   : flow_graph_(flow_graph),
     reaching_defs_(flow_graph),
@@ -522,16 +516,16 @@
         range->DefineAt(catch_entry->start_pos());  // Defined at block entry.
         ProcessInitialDefinition(defn, range, catch_entry);
       }
-      // Block the two registers used by CatchEntryInstr from the block start to
-      // until the end of the instruction so that they are preserved.
-      ASSERT(catch_entry->next()->IsCatchEntry());
+      // Block the two fixed registers used by CatchBlockEntryInstr from the
+      // block start to until the end of the instruction so that they are
+      // preserved.
       intptr_t start = catch_entry->start_pos();
       BlockLocation(Location::RegisterLocation(kExceptionObjectReg),
                     start,
-                    ToInstructionEnd(NextInstructionPos(start)));
+                    ToInstructionEnd(start));
       BlockLocation(Location::RegisterLocation(kStackTraceObjectReg),
                     start,
-                    ToInstructionEnd(NextInstructionPos(start)));
+                    ToInstructionEnd(start));
     }
   }