Relax test condition to make it less brittle.

test/cctest/test-heap.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 
 #include <stdlib.h>
 
 #include "v8.h"
 
 #include "execution.h"
 #include "factory.h"
 #include "macro-assembler.h"
 #include "global-handles.h"
@@ skipping 1272 matching lines @@
   old_capacity = new_space->Capacity();
   new_space->Grow();
   new_capacity = new_space->Capacity();
   CHECK(2 * old_capacity == new_capacity);
   FillUpNewSpace(new_space);
   HEAP->CollectAllAvailableGarbage();
   new_capacity = new_space->Capacity();
   CHECK(old_capacity == new_capacity);
 }
 
-
+// This just checks the contract of the IdleNotification() function,
+// and does not verify that it does reasonable work.
 TEST(IdleNotificationAdvancesIncrementalMarking) {
   if (!FLAG_incremental_marking || !FLAG_incremental_marking_steps) return;
   InitializeVM();
   v8::HandleScope scope;
   const char* source = "function binom(n, m) {"
                        "  var C = [[1]];"
                        "  for (var i = 1; i <= n; ++i) {"
                        "    C[i] = [1];"
                        "    for (var j = 1; j < i; ++j) {"
                        "      C[i][j] = C[i-1][j-1] + C[i-1][j];"
                        "    }"
                        "    C[i][i] = 1;"
                        "  }"
                        "  return C[n][m];"
                        "};"
                        "binom(1000, 500)";
   {
     AlwaysAllocateScope aa_scope;
     CompileRun(source);
   }
   intptr_t old_size = HEAP->SizeOfObjects();
   bool no_idle_work = v8::V8::IdleNotification(900);
   while (!v8::V8::IdleNotification(900)) ;
   intptr_t new_size = HEAP->SizeOfObjects();
-  CHECK(no_idle_work || new_size < 3 * old_size / 4);
+  CHECK(no_idle_work || new_size < old_size);
 }