Bug 1401069 - Part 2. Implement ReleaseAllResource to make WindowsEMF::InitForDrawing reusable. r=fatseng

Currently, WindowsEMF::InitForDrawing can be used once. With the change in this
patch, we can call WindowsEMF::InitForDrawing and Playback/SaveToFile in pair
as many times as we want.

MozReview-Commit-ID: 4fbY4Q6i9v5

--HG--
extra : rebase_source : 4df3fc7d8663d7f552c96204a16d73261bfc9dd7

widget/windows/WindowsEMF.cpp

@@ -17,15 +17,13 @@ WindowsEMF::WindowsEMF()
 
 WindowsEMF::~WindowsEMF()
 {
-  FinishDocument();
-  ReleaseEMFHandle();
+  ReleaseAllResource();
 }
 
 bool
 WindowsEMF::InitForDrawing(const wchar_t* aMetafilePath /* = nullptr */)
 {
-  MOZ_ASSERT(!mDC && !mEmf, "InitForDrawing and InitFromFileContents is"
-                            " designed to be used either one at once.");
+  ReleaseAllResource();
 
   mDC = ::CreateEnhMetaFile(nullptr, aMetafilePath, nullptr, nullptr);
   return !!mDC;
@@ -35,8 +33,7 @@ bool
 WindowsEMF::InitFromFileContents(const wchar_t* aMetafilePath)
 {
   MOZ_ASSERT(aMetafilePath);
-  MOZ_ASSERT(!mDC && !mEmf, "InitForDrawing and InitFromFileContents is"
-                            " designed to be used either one at once.");
+  ReleaseAllResource();
 
   mEmf = ::GetEnhMetaFileW(aMetafilePath);
   return !!mEmf;
@@ -61,6 +58,13 @@ WindowsEMF::ReleaseEMFHandle()
   }
 }
 
+void
+WindowsEMF::ReleaseAllResource()
+{
+  FinishDocument();
+  ReleaseEMFHandle();
+}
+
 bool
 WindowsEMF::Playback(HDC aDeviceContext, const RECT* aRect)
 {

widget/windows/WindowsEMF.h

@@ -69,6 +69,7 @@ private:
   WindowsEMF(const WindowsEMF& aEMF) = delete;
   bool FinishDocument();
   void ReleaseEMFHandle();
+  void ReleaseAllResource();
 
   /* Compiled EMF data handle. */
   HENHMETAFILE mEmf;