Revert "Switch on implicit null pointer and stack overflow checks."

This seems to break facebook

This reverts commit 052664322767de1799f060c306e729b0e73ce893.

Change-Id: I6c8dabdc2519c0925ffde41975878f821e3933de
diff --git a/runtime/runtime.cc b/runtime/runtime.cc
index cbd51d4..027feee 100644
--- a/runtime/runtime.cc
+++ b/runtime/runtime.cc
@@ -535,20 +535,9 @@
     GetInstrumentation()->ForceInterpretOnly();
   }
 
-  bool implicit_checks_supported = false;
-  switch (kRuntimeISA) {
-  case kArm:
-  case kThumb2:
-    implicit_checks_supported = true;
-    break;
-  default:
-    break;
-  }
-
-  if (implicit_checks_supported &&
-    (options->explicit_checks_ != (ParsedOptions::kExplicitSuspendCheck |
+  if (options->explicit_checks_ != (ParsedOptions::kExplicitSuspendCheck |
         ParsedOptions::kExplicitNullCheck |
-        ParsedOptions::kExplicitStackOverflowCheck) || kEnableJavaStackTraceHandler)) {
+        ParsedOptions::kExplicitStackOverflowCheck) || kEnableJavaStackTraceHandler) {
     fault_manager.Init();
 
     // These need to be in a specific order.  The null point check handler must be