Bug 1401888 - Part 2. Implement PDFiumEngineShim::GetInstanceOrNull(const nsCString&) r=fatseng

With this change, we are able to load PDFium engine from different library.
MozReview-Commit-ID: ErAZCPRzRR5

--HG--
extra : rebase_source : f0421af9c70d69564ed8f96d32870314871aabef

widget/windows/PDFiumEngineShim.cpp

@@ -18,7 +18,7 @@ PDFiumEngineShim::GetInstanceOrNull()
   RefPtr<PDFiumEngineShim> inst = sPDFiumEngineShim;
   if (!inst) {
     inst = new PDFiumEngineShim();
-    if (!inst->Init()) {
+    if (!inst->Init(nsCString("pdfium.dll"))) {
       inst = nullptr;
     }
     sPDFiumEngineShim = inst.get();
@@ -27,6 +27,18 @@ PDFiumEngineShim::GetInstanceOrNull()
   return inst.forget();
 }
 
+/* static */
+already_AddRefed<PDFiumEngineShim>
+PDFiumEngineShim::GetInstanceOrNull(const nsCString& aLibrary)
+{
+  RefPtr<PDFiumEngineShim> shim = new PDFiumEngineShim();
+  if (!shim->Init(aLibrary)) {
+    return nullptr;
+  }
+
+  return shim.forget();
+}
+
 PDFiumEngineShim::PDFiumEngineShim()
   : mFPDF_InitLibrary(nullptr)
   , mFPDF_DestroyLibrary(nullptr)
@@ -54,13 +66,13 @@ PDFiumEngineShim::~PDFiumEngineShim()
 }
 
 bool
-PDFiumEngineShim::Init()
+PDFiumEngineShim::Init(const nsCString& aLibrary)
 {
   if (mInitialized) {
     return true;
   }
 
-  mPRLibrary = PR_LoadLibrary("pdfium.dll");
+  mPRLibrary = PR_LoadLibrary(aLibrary.get());
   NS_ENSURE_TRUE(mPRLibrary, false);
 
   mFPDF_InitLibrary = (FPDF_InitLibrary_Pfn)PR_FindFunctionSymbol(

widget/windows/PDFiumEngineShim.h

@@ -48,6 +48,10 @@ public:
   NS_INLINE_DECL_THREADSAFE_REFCOUNTING(PDFiumEngineShim)
 
   static already_AddRefed<PDFiumEngineShim> GetInstanceOrNull();
+  // This function is used for testing purpose only, do not call it in regular
+  // code.
+  static already_AddRefed<PDFiumEngineShim>
+  GetInstanceOrNull(const nsCString& aLibrary);
 
   FPDF_DOCUMENT LoadDocument(FPDF_STRING file_path,
                              FPDF_BYTESTRING aPassword);
@@ -66,7 +70,7 @@ public:
 private:
   PDFiumEngineShim();
   ~PDFiumEngineShim();
-  bool Init();
+  bool Init(const nsCString& aLibrary);
 
   bool        mInitialized ;