Fix float conversion warning from some gcc versions.

test/cctest/test-serialize.cc

 // Copyright 2007-2008 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * 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
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 270 matching lines @@
 
 TEST(LinearAllocation) {
   v8::V8::Initialize();
   NewSpace* new_space = Heap::new_space();
   PagedSpace* old_pointer_space = Heap::old_pointer_space();
   PagedSpace* old_data_space = Heap::old_data_space();
   PagedSpace* code_space = Heap::code_space();
   PagedSpace* map_space = Heap::map_space();
   PagedSpace* cell_space = Heap::cell_space();
   int new_space_max = 512 * KB;
-  for (int size = 1000; size < 5 * MB; size *= 1.5) {
+  for (int size = 1000; size < 5 * MB; size += size >> 1) {
     bool gc_performed = true;
     while (gc_performed) {
       gc_performed = false;
       if (size < new_space_max) {
         if (!new_space->ReserveSpace(size)) {
           Heap::CollectGarbage(size, NEW_SPACE);
           gc_performed = true;
           CHECK(new_space->ReserveSpace(size));
         }
       }
@@ skipping 119 matching lines @@
 TEST(TestThatAlwaysFails) {
   bool ArtificialFailure = false;
   CHECK(ArtificialFailure);
 }
 
 
 DEPENDENT_TEST(DependentTestThatAlwaysFails, TestThatAlwaysSucceeds) {
   bool ArtificialFailure2 = false;
   CHECK(ArtificialFailure2);
 }