Rename CPDFDoc_Environment to CPDFSDK_Environment

CPDFDoc_Environment does not fit with the general naming scheme of the rest of
the files in fpdfsdk. This CL updates the naming to CPDFSDK_Environment to
better fit with the surrounding files.

Review-Url: https://codereview.chromium.org/2333413003
diff --git a/fpdfsdk/javascript/JS_Runtime_Stub.cpp b/fpdfsdk/javascript/JS_Runtime_Stub.cpp
index 2b4a624..2c7eda8 100644
--- a/fpdfsdk/javascript/JS_Runtime_Stub.cpp
+++ b/fpdfsdk/javascript/JS_Runtime_Stub.cpp
@@ -163,6 +163,6 @@
 void IJS_Runtime::Destroy() {}
 
 // static
-IJS_Runtime* IJS_Runtime::Create(CPDFDoc_Environment* pEnv) {
+IJS_Runtime* IJS_Runtime::Create(CPDFSDK_Environment* pEnv) {
   return new CJS_RuntimeStub;
 }