PolicyManager: Dump EvaluationContext on test failure.

This patch dumps the value of the used variables on a test when the
ExpectPolicyStatus() call fails.

BUG=None
TEST=Modified a test to make it fail and dump the results.

Change-Id: I0ce7768256ac05cd2522c36569d74312463ac293
Reviewed-on: https://chromium-review.googlesource.com/200434
Reviewed-by: Alex Deymo <deymo@chromium.org>
Commit-Queue: Alex Deymo <deymo@chromium.org>
Tested-by: Alex Deymo <deymo@chromium.org>
diff --git a/policy_manager/chromeos_policy_unittest.cc b/policy_manager/chromeos_policy_unittest.cc
index c4968ad..265a279 100644
--- a/policy_manager/chromeos_policy_unittest.cc
+++ b/policy_manager/chromeos_policy_unittest.cc
@@ -58,8 +58,8 @@
     eval_ctx_->ResetEvaluation();
     EXPECT_EQ(expected,
               (policy_.*policy_method)(eval_ctx_, &fake_state_, &error, result))
-        << "Returned error: " << error;
-    // TODO(deymo): Dump the context of the EvaluationContext on failure.
+        << "Returned error: " << error
+        << "\nEvaluation context: " << eval_ctx_->DumpContext();
   }
 
   FakeClock fake_clock_;