Down integrate from Google internal.

google/protobuf/any.proto

@@ -110,6 +110,8 @@ message Any {
   // * If no schema is provided, `https` is assumed.
   // * The last segment of the URL's path must represent the fully
   //   qualified name of the type (as in `path/google.protobuf.Duration`).
+  //   The name should be in a canonical form (e.g., leading "." is
+  //   not accepted).
   // * An HTTP GET on the URL must yield a [google.protobuf.Type][]
   //   value in binary format, or produce an error.
   // * Applications are allowed to cache lookup results based on the

google/protobuf/field_mask.proto

@@ -88,7 +88,7 @@ option java_generate_equals_and_hash = true;
 // operation applies to all fields (as if a FieldMask of all fields
 // had been specified).
 //
-// Note that a field mask does not necessarily applies to the
+// Note that a field mask does not necessarily apply to the
 // top-level response message. In case of a REST get operation, the
 // field mask applies directly to the response, but in case of a REST
 // list operation, the mask instead applies to each individual message

google/protobuf/util/internal/testdata/books.proto

@@ -176,3 +176,12 @@ message NestedBook {
 message BadNestedBook {
   repeated uint32 book = 1 [packed=true];  // Packed to optional message.
 }
+
+// A recursively defined message.
+message Cyclic {
+  optional int32 m_int = 1;
+  optional string m_str = 2;
+  optional Book m_book = 3;
+  repeated Author m_author = 5;
+  optional Cyclic m_cyclic = 4;
+}