[cpu-profiler] Fix flaky MultipleIsolates test

This test is only flaky because the js code being profiled causes a
'fast-c-call' which is a call from JS to C without an exit frame.

The profiler stumbles on these and reads the stack of C++ frames when
it shouldn't, causing ASAN errors. This is not actually related to
the multiple isolates, so I'm changing the test to profile different
JS code that does not cause these types of calls. There is already a
test for fast-c-calls - NativeFrameStackTrace (which currently fails).

Bug: v8:8464
Change-Id: I32818f0894e5680cf5a39779a2779eda36dfe9f1
Reviewed-on: https://chromium-review.googlesource.com/c/1337571
Commit-Queue: Peter Marshall <petermarshall@chromium.org>
Reviewed-by: Yang Guo <yangguo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#57547}

test/cctest/cctest.status

@@ -91,7 +91,6 @@
   'test-cpu-profiler/NativeAccessorUninitializedIC': [SKIP],
   'test-cpu-profiler/SampleWhenFrameIsNotSetup': [SKIP],
   'test-cpu-profiler/TracingCpuProfiler': [SKIP],
-  'test-cpu-profiler/MultipleIsolates': [SKIP],
   'test-sampler/LibSamplerCollectSample': [SKIP],
 
   # BUG(7202). The test is flaky.

test/cctest/test-cpu-profiler.cc

@@ -2560,12 +2560,13 @@ void ProfileSomeCode(v8::Isolate* isolate) {
   profiler->StartProfiling(profile_name);
   const char* source = R"(
       function foo() {
-        var s = {};
-        for (var i = 0; i < 1e4; ++i) {
-          for (var j = 0; j < 100; j++) {
-            s['item' + j] = 'bar';
+        var x = 0;
+        for (var i = 0; i < 1e4; i++) {
+          for (var j = 0; j < 1e3; j++) {
+            x += i * j;
           }
         }
+        return x;
       }
       foo();
     )";