Fix delta computation in DoDeferredInstanceOfKnownGlobal() for ARM.

test/mjsunit/mjsunit.status

 # Copyright 2012 the V8 project authors. All rights reserved.
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 # modification, are permitted provided that the following conditions are
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 #
 #     * Redistributions of source code must retain the above copyright
 #       notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
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@@ skipping 69 matching lines @@
 # Flaky test that can hit compilation-time stack overflow in debug mode.
 unicode-test: PASS, (PASS || FAIL) if $mode == debug
 
 # Times out often in release mode on ARM.
 compiler/regress-stacktrace-methods: PASS, PASS || TIMEOUT if $mode == release
 array-splice: PASS || TIMEOUT
 
 # Long running test.
 string-indexof-2: PASS || TIMEOUT
 # BUG(2314): Crankshaft generates incorrect (crashing) code on ARM
-# mirror-object: PASS || TIMEOUT
-mirror-object: SKIP
+mirror-object: PASS || TIMEOUT
 
 # BUG(3251035): Timeouts in long looping crankshaft optimization
 # tests. Skipping because having them timeout takes too long on the
 # buildbot.
 compiler/alloc-number: SKIP
 compiler/array-length: SKIP
 compiler/assignment-deopt: SKIP
 compiler/deopt-args: SKIP
 compiler/inline-compare: SKIP
 compiler/inline-global-access: SKIP
@@ skipping 78 matching lines @@
 # the test requires too much time to run.  However, the problem test covers
 # should be platform-independent.
 regress/regress-1132: SKIP
 
 # Stack manipulations in LiveEdit is not implemented for this arch.
 debug-liveedit-check-stack: SKIP
 debug-liveedit-stack-padding: SKIP
 debug-liveedit-restart-frame: SKIP
 debug-liveedit-double-call: SKIP