Add scoped_ptr-safe base::Value to Dictionary/List conversion functions.

This change adds two static From() functions to the DictionaryValue and
ListValue classes which take a scoped_ptr to a Value and either convert
it to a scoped_ptr to a DictionaryValue or ListValue, or return nullptr.
These are intended to replace the existing pattern,

  make_scoped_ptr(static_cast<base::DictionaryValue*>(value.release()))

with the shorter and safer alternative,

  base::DictionaryValue::From(value.Pass())

Instances of this pattern in //extensions have been converted as
examples.

Review URL: https://codereview.chromium.org/1308013005

Cr-Commit-Position: refs/heads/master@{#348294}

1 files changed, 4 insertions, 6 deletions

diff --git a/extensions/renderer/guest_view/guest_view_internal_custom_bindings.cc b/extensions/renderer/guest_view/guest_view_internal_custom_bindings.cc
index 3b5ce79..7eb1292 100644
--- a/extensions/renderer/guest_view/guest_view_internal_custom_bindings.cc
+++ b/extensions/renderer/guest_view/guest_view_internal_custom_bindings.cc
@@ -151,9 +151,8 @@ void GuestViewInternalCustomBindings::AttachGuest(
     scoped_ptr<V8ValueConverter> converter(V8ValueConverter::create());
     scoped_ptr<base::Value> params_as_value(
         converter->FromV8Value(args[2], context()->v8_context()));
-    CHECK(params_as_value->IsType(base::Value::TYPE_DICTIONARY));
-    params.reset(
-        static_cast<base::DictionaryValue*>(params_as_value.release()));
+    params = base::DictionaryValue::From(params_as_value.Pass());
+    CHECK(params);
   }
 
   // Add flag to |params| to indicate that the element size is specified in
@@ -226,9 +225,8 @@ void GuestViewInternalCustomBindings::AttachIframeGuest(
     scoped_ptr<V8ValueConverter> converter(V8ValueConverter::create());
     scoped_ptr<base::Value> params_as_value(
         converter->FromV8Value(args[2], context()->v8_context()));
-    CHECK(params_as_value->IsType(base::Value::TYPE_DICTIONARY));
-    params.reset(
-        static_cast<base::DictionaryValue*>(params_as_value.release()));
+    params = base::DictionaryValue::From(params_as_value.Pass());
+    CHECK(params);
   }
 
   // Add flag to |params| to indicate that the element size is specified in