Migrated several tests from blink to V8 repository.

test/webkit/dfg-double-use-of-post-simplification-double-prediction.js

Index: test/webkit/dfg-double-use-of-post-simplification-double-prediction.js
diff --git a/test/webkit/concat-while-having-a-bad-time.js b/test/webkit/dfg-double-use-of-post-simplification-double-prediction.js
similarity index 81%
copy from test/webkit/concat-while-having-a-bad-time.js
copy to test/webkit/dfg-double-use-of-post-simplification-double-prediction.js
index dfda1e08a0b36194b787a44ee12a9693acd8aeaf..cf385791c021f4f70ad99d804f290515f72cc853 100644
--- a/test/webkit/concat-while-having-a-bad-time.js
+++ b/test/webkit/dfg-double-use-of-post-simplification-double-prediction.js
@@ -22,10 +22,19 @@
 // SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 description(
-"Tests the behavior of Array.prototype.concat while the array is having a bad time due to one of the elements we are concatenating."
+"Tests stability of the DFG compiler when you have a double use of a variable that is not revealed to be a double until after CFG simplification."
 );
 
-Object.defineProperty(Array.prototype, 0, { writable: false });
-shouldBe("[42].concat()", "[42]");
+function foo(a) {
+    var p = true;
+    var x;
+    if (p)
+        x = 42;
+    else
+        x = "yo";
+    return x + a;
+}
 
+for (var i = 0; i < 200; ++i)
+    shouldBe("foo(0.5)", "42.5");