Oilpan: Allow clearing a vector during pre finalizer to disallocate the backing buffer

third_party/WebKit/Source/platform/heap/HeapTest.cpp

Index: third_party/WebKit/Source/platform/heap/HeapTest.cpp
diff --git a/third_party/WebKit/Source/platform/heap/HeapTest.cpp b/third_party/WebKit/Source/platform/heap/HeapTest.cpp
index 0448e3b7b4bf482d2a6ef4fad9e8fb7a3f516bf5..24117da61ad706840be77d247d045d14dc0127e4 100644
--- a/third_party/WebKit/Source/platform/heap/HeapTest.cpp
+++ b/third_party/WebKit/Source/platform/heap/HeapTest.cpp
@@ -1517,12 +1517,15 @@ class PreFinalizerBackingShrinkForbidden
   }
 
   void Dispose() {
-    // Remove elemets so that vector_ will try to shrink.
-    for (int i = 0; i < 32; ++i) {
+    // Remove all elemets except one so that vector_ will try to shrink.
+    for (int i = 1; i < 32; ++i) {
       vector_.pop_back();
     }
     // Check that vector_ hasn't shrunk.
-    EXPECT_LT(31ul, map_.Capacity());
+    EXPECT_LT(31ul, vector_.Capacity());
+    // Just releasing the backing is allowed.
+    vector_.Clear();
+    EXPECT_EQ(0ul, vector_.Capacity());
 
     // Remove elemets so that map_ will try to shrink.
     for (int i = 0; i < 32; ++i) {