Cleanup unused methods and return values in FWL code.

xfa/fwl/theme/cfwl_datetimepickertp.cpp

Index: xfa/fwl/theme/cfwl_datetimepickertp.cpp
diff --git a/xfa/fwl/theme/cfwl_datetimepickertp.cpp b/xfa/fwl/theme/cfwl_datetimepickertp.cpp
index 36738d9a59675630e4ca8cf3b45291833cf04827..f6eb3b364a6dec5313b0b4dfbef0169dd2363588 100644
--- a/xfa/fwl/theme/cfwl_datetimepickertp.cpp
+++ b/xfa/fwl/theme/cfwl_datetimepickertp.cpp
@@ -17,9 +17,10 @@ bool CFWL_DateTimePickerTP::IsValidWidget(IFWL_Widget* pWidget) {
   return pWidget && pWidget->GetClassID() == FWL_Type::DateTimePicker;
 }
 
-FX_BOOL CFWL_DateTimePickerTP::DrawBackground(CFWL_ThemeBackground* pParams) {
+void CFWL_DateTimePickerTP::DrawBackground(CFWL_ThemeBackground* pParams) {
   if (!pParams)
-    return FALSE;
+    return;
+
   switch (pParams->m_iPart) {
     case CFWL_Part::Border: {
       DrawBorder(pParams->m_pGraphics, &pParams->m_rtPart, &pParams->m_matrix);
@@ -34,9 +35,9 @@ FX_BOOL CFWL_DateTimePickerTP::DrawBackground(CFWL_ThemeBackground* pParams) {
       DrawDropDownButton(pParams, &pParams->m_matrix);
       break;
     }
-    default: {}
+    default:
+      break;
   }
-  return TRUE;
 }
 
 void CFWL_DateTimePickerTP::DrawDropDownButton(CFWL_ThemeBackground* pParams,
@@ -61,7 +62,8 @@ void CFWL_DateTimePickerTP::DrawDropDownButton(CFWL_ThemeBackground* pParams,
       eState = FWLTHEME_STATE_Disabale;
       break;
     }
-    default: {}
+    default:
+      break;
   }
   DrawArrowBtn(pParams->m_pGraphics, &pParams->m_rtPart,
                FWLTHEME_DIRECTION_Down, eState, pMatrix);