Change bool type to fix warnings.

fpdfsdk/cfx_systemhandler.cpp

Index: fpdfsdk/cfx_systemhandler.cpp
diff --git a/fpdfsdk/cfx_systemhandler.cpp b/fpdfsdk/cfx_systemhandler.cpp
index 95a940d1ff02c0b41ba6ac9c4c27c5ab94fb5ba9..c5f53341e18161a50424200d40ac529602c49696 100644
--- a/fpdfsdk/cfx_systemhandler.cpp
+++ b/fpdfsdk/cfx_systemhandler.cpp
@@ -126,17 +126,13 @@ FX_SYSTEMTIME CFX_SystemHandler::GetLocalTime() {
 }
 
 bool CFX_SystemHandler::IsSHIFTKeyDown(uint32_t nFlag) const {
-  return m_pEnv->FFI_IsSHIFTKeyDown(nFlag);
+  return !!m_pEnv->FFI_IsSHIFTKeyDown(nFlag);
 }
 
 bool CFX_SystemHandler::IsCTRLKeyDown(uint32_t nFlag) const {
-  return m_pEnv->FFI_IsCTRLKeyDown(nFlag);
+  return !!m_pEnv->FFI_IsCTRLKeyDown(nFlag);
 }
 
 bool CFX_SystemHandler::IsALTKeyDown(uint32_t nFlag) const {
-  return m_pEnv->FFI_IsALTKeyDown(nFlag);
-}
-
-bool CFX_SystemHandler::IsINSERTKeyDown(uint32_t nFlag) const {
-  return m_pEnv->FFI_IsINSERTKeyDown(nFlag);
+  return !!m_pEnv->FFI_IsALTKeyDown(nFlag);
 }