Inline CFX_WideString::c_str.

This was causing issues at one point with the GN build but seems to have been
resolved in the meantime.

Review URL: https://codereview.chromium.org/1907563002

core/fxcrt/fx_basic_wstring.cpp

diff --git a/core/fxcrt/fx_basic_wstring.cpp b/core/fxcrt/fx_basic_wstring.cpp
index 1e8f1f3..069b9fa 100644
--- a/core/fxcrt/fx_basic_wstring.cpp
+++ b/core/fxcrt/fx_basic_wstring.cpp
@@ -579,10 +579,6 @@
   va_end(argListSave);
 }
 
-const FX_WCHAR* CFX_WideString::c_str() const {
-  return m_pData ? m_pData->m_String : L"";
-}
-
 void CFX_WideString::Format(const FX_WCHAR* pFormat, ...) {
   va_list argList;
   va_start(argList, pFormat);

core/fxcrt/include/fx_string.h

diff --git a/core/fxcrt/include/fx_string.h b/core/fxcrt/include/fx_string.h
index 8041522..10a70d9 100644
--- a/core/fxcrt/include/fx_string.h
+++ b/core/fxcrt/include/fx_string.h
@@ -496,7 +496,7 @@
 
   // Explicit conversion to C-style wide string.
   // Note: Any subsequent modification of |this| will invalidate the result.
-  const FX_WCHAR* c_str() const;
+  const FX_WCHAR* c_str() const { return m_pData ? m_pData->m_String : L""; }
 
   // Explicit conversion to CFX_WideStringC.
   // Note: Any subsequent modification of |this| will invalidate the result.