Fix scope resolution for Google namespace

src/google/protobuf/compiler/ruby/ruby_generated_code_pb.rb

@@ -68,9 +68,9 @@ end
 module A
   module B
     module C
-      TestMessage = Google::Protobuf::DescriptorPool.generated_pool.lookup("A.B.C.TestMessage").msgclass
-      TestMessage::NestedMessage = Google::Protobuf::DescriptorPool.generated_pool.lookup("A.B.C.TestMessage.NestedMessage").msgclass
-      TestEnum = Google::Protobuf::DescriptorPool.generated_pool.lookup("A.B.C.TestEnum").enummodule
+      TestMessage = ::Google::Protobuf::DescriptorPool.generated_pool.lookup("A.B.C.TestMessage").msgclass
+      TestMessage::NestedMessage = ::Google::Protobuf::DescriptorPool.generated_pool.lookup("A.B.C.TestMessage.NestedMessage").msgclass
+      TestEnum = ::Google::Protobuf::DescriptorPool.generated_pool.lookup("A.B.C.TestEnum").enummodule
     end
   end
 end

src/google/protobuf/compiler/ruby/ruby_generated_code_proto2_pb.rb

@@ -69,9 +69,9 @@ end
 module A
   module B
     module C
-      TestMessage = Google::Protobuf::DescriptorPool.generated_pool.lookup("A.B.C.TestMessage").msgclass
-      TestMessage::NestedMessage = Google::Protobuf::DescriptorPool.generated_pool.lookup("A.B.C.TestMessage.NestedMessage").msgclass
-      TestEnum = Google::Protobuf::DescriptorPool.generated_pool.lookup("A.B.C.TestEnum").enummodule
+      TestMessage = ::Google::Protobuf::DescriptorPool.generated_pool.lookup("A.B.C.TestMessage").msgclass
+      TestMessage::NestedMessage = ::Google::Protobuf::DescriptorPool.generated_pool.lookup("A.B.C.TestMessage.NestedMessage").msgclass
+      TestEnum = ::Google::Protobuf::DescriptorPool.generated_pool.lookup("A.B.C.TestEnum").enummodule
     end
   end
 end

src/google/protobuf/compiler/ruby/ruby_generated_pkg_explicit_legacy_pb.rb

@@ -14,7 +14,7 @@ end
 module AA
   module BB
     module CC
-      Four = Google::Protobuf::DescriptorPool.generated_pool.lookup("one.two.a_three.and.Four").msgclass
+      Four = ::Google::Protobuf::DescriptorPool.generated_pool.lookup("one.two.a_three.and.Four").msgclass
     end
   end
 end

src/google/protobuf/compiler/ruby/ruby_generated_pkg_explicit_pb.rb

@@ -14,7 +14,7 @@ end
 module A
   module B
     module C
-      Four = Google::Protobuf::DescriptorPool.generated_pool.lookup("one.two.a_three.Four").msgclass
+      Four = ::Google::Protobuf::DescriptorPool.generated_pool.lookup("one.two.a_three.Four").msgclass
     end
   end
 end

src/google/protobuf/compiler/ruby/ruby_generated_pkg_implicit_pb.rb

@@ -14,7 +14,7 @@ end
 module One
   module Two
     module AThree
-      Four = Google::Protobuf::DescriptorPool.generated_pool.lookup("one.two.a_three.Four").msgclass
+      Four = ::Google::Protobuf::DescriptorPool.generated_pool.lookup("one.two.a_three.Four").msgclass
     end
   end
 end

src/google/protobuf/compiler/ruby/ruby_generator.cc

@@ -371,7 +371,7 @@ void GenerateMessageAssignment(const std::string& prefix,
     "prefix", prefix,
     "name", RubifyConstant(message->name()));
   printer->Print(
-    "Google::Protobuf::DescriptorPool.generated_pool."
+    "::Google::Protobuf::DescriptorPool.generated_pool."
     "lookup(\"$full_name$\").msgclass\n",
     "full_name", message->full_name());
 
@@ -391,7 +391,7 @@ void GenerateEnumAssignment(const std::string& prefix, const EnumDescriptor* en,
     "prefix", prefix,
     "name", RubifyConstant(en->name()));
   printer->Print(
-    "Google::Protobuf::DescriptorPool.generated_pool."
+    "::Google::Protobuf::DescriptorPool.generated_pool."
     "lookup(\"$full_name$\").enummodule\n",
     "full_name", en->full_name());
 }