Rename CPDFSDK_Environment to CPDFSDK_FormfillEnvironment

Rename CPDFSDK_Environment to make it explicit that this is part of the formfill
system.

Review-Url: https://codereview.chromium.org/2391313002
diff --git a/fpdfsdk/javascript/JS_GlobalData.cpp b/fpdfsdk/javascript/JS_GlobalData.cpp
index c07fe24..4e3782e 100644
--- a/fpdfsdk/javascript/JS_GlobalData.cpp
+++ b/fpdfsdk/javascript/JS_GlobalData.cpp
@@ -40,7 +40,8 @@
 }  // namespace
 
 // static
-CJS_GlobalData* CJS_GlobalData::GetRetainedInstance(CPDFSDK_Environment* pApp) {
+CJS_GlobalData* CJS_GlobalData::GetRetainedInstance(
+    CPDFSDK_FormFillEnvironment* pApp) {
   if (!g_pInstance) {
     g_pInstance = new CJS_GlobalData();
   }