Request text context in the plugin process

ppapi/proxy/ppb_text_input_proxy.cc

Index: ppapi/proxy/ppb_text_input_proxy.cc
diff --git a/ppapi/proxy/ppb_text_input_proxy.cc b/ppapi/proxy/ppb_text_input_proxy.cc
index e7434e07e68bcf07abcd9475da3db7f3ef69c661..3d2f873ba48ec8b2d58245d0e69eea838feadcd6 100644
--- a/ppapi/proxy/ppb_text_input_proxy.cc
+++ b/ppapi/proxy/ppb_text_input_proxy.cc
@@ -6,12 +6,32 @@
 
 #include "ppapi/proxy/plugin_dispatcher.h"
 #include "ppapi/proxy/ppapi_messages.h"
+#include "ppapi/shared_impl/ppb_instance_shared.h"
 #include "ppapi/thunk/enter.h"
 #include "ppapi/thunk/thunk.h"
 
 namespace ppapi {
 namespace proxy {
 
+namespace {
+
+void RequestSurroundingText(PP_Instance instance) {
+  PluginDispatcher* dispatcher = PluginDispatcher::GetForInstance(instance);
+  if (!dispatcher)
+    return;  // Instance has gone away while message was pending.
+
+  // Just fake out a RequestSurroundingText message to the proxy for the PPP
+  // interface.
+  InterfaceProxy* proxy = dispatcher->GetInterfaceProxy(API_ID_PPB_TEXT_INPUT);
+  if (!proxy)
+    return;
+  proxy->OnMessageReceived(PpapiMsg_PPPTextInput_RequestSurroundingText(
+      API_ID_PPP_TEXT_INPUT, instance,
+      PPB_Instance_Shared::kExtraCharsForTextInput));
+}
+
+}  // namespace
+
 PPB_TextInput_Proxy::PPB_TextInput_Proxy(Dispatcher* dispatcher)
     : InterfaceProxy(dispatcher) {
 }
@@ -43,8 +63,19 @@ void PPB_TextInput_Proxy::CancelCompositionText(PP_Instance instance) {
 }
 
 void PPB_TextInput_Proxy::SelectionChanged(PP_Instance instance) {
-  dispatcher()->Send(new PpapiHostMsg_PPBTextInput_SelectionChanged(
-      API_ID_PPB_TEXT_INPUT, instance));
+  // The "right" way to do this is to send the message to the host. However,
+  // all it will do it call RequestSurroundingText with a hardcoded number of
+  // characters in response, which is an entire IPC round-trip.
+  //
+  // We can avoid this round-trip by just implementing the
+  // RequestSurroundingText logic in the plugin process. If the logic in the
+  // host becomes more complex (like a more adaptive number of characters),
+  // we'll need to reevanuate whether we want to do the round trip instead.
+  //
+  // Be careful to post a task to avoid reentering the plugin.
+  MessageLoop::current()->PostTask(
+      FROM_HERE,
+      base::Bind(&RequestSurroundingText, instance));
 }
 
 void PPB_TextInput_Proxy::UpdateSurroundingText(PP_Instance instance,
@@ -64,8 +95,6 @@ bool PPB_TextInput_Proxy::OnMessageReceived(const IPC::Message& msg) {
                         OnMsgUpdateCaretPosition)
     IPC_MESSAGE_HANDLER(PpapiHostMsg_PPBTextInput_CancelCompositionText,
                         OnMsgCancelCompositionText)
-    IPC_MESSAGE_HANDLER(PpapiHostMsg_PPBTextInput_SelectionChanged,
-                        OnMsgSelectionChanged)
     IPC_MESSAGE_HANDLER(PpapiHostMsg_PPBTextInput_UpdateSurroundingText,
                         OnMsgUpdateSurroundingText)
     IPC_MESSAGE_UNHANDLED(handled = false)
@@ -97,13 +126,6 @@ void PPB_TextInput_Proxy::OnMsgCancelCompositionText(PP_Instance instance) {
     enter.functions()->CancelCompositionText(instance);
 }
 
-void PPB_TextInput_Proxy::OnMsgSelectionChanged(PP_Instance instance) {
-  ppapi::thunk::EnterFunctionNoLock<PPB_TextInput_FunctionAPI> enter(instance,
-                                                                     true);
-  if (enter.succeeded())
-    enter.functions()->SelectionChanged(instance);
-}
-
 void PPB_TextInput_Proxy::OnMsgUpdateSurroundingText(PP_Instance instance,
                                                      const std::string& text,
                                                      uint32_t caret,