base: Fix an inefficiency in base::Pickle that caused extraneous allocations.

base/pickle_unittest.cc

Index: base/pickle_unittest.cc
diff --git a/base/pickle_unittest.cc b/base/pickle_unittest.cc
index b0a8f21f89f9282d5d6783eaf13d49e43f837a6e..6f9fcc7f62ad898bf4b7de91aee43faafddbda6d 100644
--- a/base/pickle_unittest.cc
+++ b/base/pickle_unittest.cc
@@ -428,4 +428,18 @@ TEST(PickleTest, ReadBytes) {
   EXPECT_EQ(data, outdata);
 }
 
+// Checks that when a pickle is deep-copied, the result is not larger than
+// needed.
+TEST(PickleTest, DeepCopyResize) {
+  Pickle pickle;
+  while (pickle.capacity_after_header() != pickle.payload_size())
+    pickle.WriteBool(true);
+
+  // Make a deep copy.
+  Pickle pickle2(pickle);
+
+  // Check that there isn't any extraneous capacity.
+  EXPECT_EQ(pickle.capacity_after_header(), pickle2.capacity_after_header());
+}
+
 }  // namespace base