Merge to XFA: Make FPDF_WIDESTRING work regardless of endianness.

Original Review URL: https://codereview.chromium.org/1554363002 .
(cherry picked from commit ed34cdf99d5a4b33e57f81f9244a311f6fb86db3)

TBR=thestig@chromium.org

Review URL: https://codereview.chromium.org/1559373002 .
diff --git a/fpdfsdk/src/fpdfdoc_embeddertest.cpp b/fpdfsdk/src/fpdfdoc_embeddertest.cpp
index 38a3662..260f25f 100644
--- a/fpdfsdk/src/fpdfdoc_embeddertest.cpp
+++ b/fpdfsdk/src/fpdfdoc_embeddertest.cpp
@@ -7,6 +7,7 @@
 #include "public/fpdfview.h"
 #include "testing/embedder_test.h"
 #include "testing/fx_string_testhelpers.h"
+#include "testing/test_support.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 class FPDFDocEmbeddertest : public EmbedderTest {};
@@ -101,20 +102,28 @@
 }
 
 TEST_F(FPDFDocEmbeddertest, FindBookmarks) {
-  // Open a file with two bookmarks, and extract the first.
+  // Open a file with two bookmarks.
   EXPECT_TRUE(OpenDocument("bookmarks.pdf"));
 
-  unsigned short buf[128];
-  FPDF_BOOKMARK child = FPDFBookmark_GetFirstChild(document(), nullptr);
+  // Find the first one, based on its known title.
+  FPDF_WIDESTRING title = GetFPDFWideString(L"A Good Beginning");
+  FPDF_BOOKMARK child = FPDFBookmark_Find(document(), title);
   EXPECT_NE(nullptr, child);
+
+  // Check that the string matches.
+  unsigned short buf[128];
   EXPECT_EQ(34, FPDFBookmark_GetTitle(child, buf, sizeof(buf)));
   EXPECT_EQ(CFX_WideString(L"A Good Beginning"),
             CFX_WideString::FromUTF16LE(buf, 16));
 
-  // Find the same one again using the title.
-  EXPECT_EQ(child, FPDFBookmark_Find(document(), buf));
+  // Check that it is them same as the one returned by GetFirstChild.
+  EXPECT_EQ(child, FPDFBookmark_GetFirstChild(document(), nullptr));
 
   // Try to find one using a non-existent title.
-  buf[0] = 'X';
-  EXPECT_EQ(nullptr, FPDFBookmark_Find(document(), buf));
+  FPDF_WIDESTRING bad_title = GetFPDFWideString(L"A BAD Beginning");
+  EXPECT_EQ(nullptr, FPDFBookmark_Find(document(), bad_title));
+
+  // Alas, the typedef includes the "const".
+  free(const_cast<unsigned short*>(title));
+  free(const_cast<unsigned short*>(bad_title));
 }
diff --git a/fpdfsdk/src/fpdftext_embeddertest.cpp b/fpdfsdk/src/fpdftext_embeddertest.cpp
index 6c1ae4c..3772686 100644
--- a/fpdfsdk/src/fpdftext_embeddertest.cpp
+++ b/fpdfsdk/src/fpdftext_embeddertest.cpp
@@ -5,6 +5,7 @@
 #include "public/fpdf_text.h"
 #include "public/fpdfview.h"
 #include "testing/embedder_test.h"
+#include "testing/test_support.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace {
@@ -143,11 +144,10 @@
   FPDF_TEXTPAGE textpage = FPDFText_LoadPage(page);
   EXPECT_NE(nullptr, textpage);
 
-  // Avoid issues with system wchar_t width vs. FPDF_WideString.
-  const unsigned short nope[] = {'n', 'o', 'p', 'e', '\0'};
-  const unsigned short world[] = {'w', 'o', 'r', 'l', 'd', '\0'};
-  const unsigned short world_caps[] = {'W', 'O', 'R', 'L', 'D', '\0'};
-  const unsigned short world_substr[] = {'o', 'r', 'l', 'd', '\0'};
+  FPDF_WIDESTRING nope = GetFPDFWideString(L"nope");
+  FPDF_WIDESTRING world = GetFPDFWideString(L"world");
+  FPDF_WIDESTRING world_caps = GetFPDFWideString(L"WORLD");
+  FPDF_WIDESTRING world_substr = GetFPDFWideString(L"orld");
 
   // No occurences of "nope" in test page.
   FPDF_SCHHANDLE search = FPDFText_FindStart(textpage, nope, 0, 0);
@@ -239,6 +239,12 @@
 
   FPDFText_ClosePage(textpage);
   UnloadPage(page);
+
+  // Alas, the typedef includes the "const".
+  free(const_cast<unsigned short*>(nope));
+  free(const_cast<unsigned short*>(world));
+  free(const_cast<unsigned short*>(world_caps));
+  free(const_cast<unsigned short*>(world_substr));
 }
 
 // Test that the page has characters despite a bad stream length.
diff --git a/samples/pdfium_test.cc b/samples/pdfium_test.cc
index 112e780..6bf1ec1 100644
--- a/samples/pdfium_test.cc
+++ b/samples/pdfium_test.cc
@@ -196,7 +196,7 @@
 
 int ExampleAppAlert(IPDF_JSPLATFORM*, FPDF_WIDESTRING msg, FPDF_WIDESTRING,
                     int, int) {
-  std::wstring platform_string = GetWideString(msg);
+  std::wstring platform_string = GetPlatformWString(msg);
   printf("Alert: %ls\n", platform_string.c_str());
   return 0;
 }
diff --git a/testing/embedder_test_timer_handling_delegate.h b/testing/embedder_test_timer_handling_delegate.h
index 74e346e..a704bd4 100644
--- a/testing/embedder_test_timer_handling_delegate.h
+++ b/testing/embedder_test_timer_handling_delegate.h
@@ -21,8 +21,8 @@
                   int type_in,
                   int icon_in)
         : type(type_in), icon(icon_in) {
-      message = GetWideString(message_in);
-      title = GetWideString(title_in);
+      message = GetPlatformWString(message_in);
+      title = GetPlatformWString(title_in);
     }
 
     std::wstring message;
diff --git a/testing/test_support.cpp b/testing/test_support.cpp
index f71f6f8..c7ab10e 100644
--- a/testing/test_support.cpp
+++ b/testing/test_support.cpp
@@ -98,7 +98,7 @@
   return buffer;
 }
 
-std::wstring GetWideString(FPDF_WIDESTRING wstr) {
+std::wstring GetPlatformWString(FPDF_WIDESTRING wstr) {
   if (!wstr)
     return nullptr;
 
@@ -114,6 +114,19 @@
   return platform_string;
 }
 
+FPDF_WIDESTRING GetFPDFWideString(const std::wstring& wstr) {
+  size_t length = sizeof(uint16_t) * (wstr.length() + 1);
+  unsigned char* ptr = static_cast<unsigned char*>(malloc(length));
+  size_t i = 0;
+  for (wchar_t w : wstr) {
+    ptr[i++] = w & 0xff;
+    ptr[i++] = (w >> 8) & 0xff;
+  }
+  ptr[i++] = 0;
+  ptr[i] = 0;
+  return reinterpret_cast<FPDF_WIDESTRING>(ptr);
+}
+
 #ifdef PDF_ENABLE_V8
 #ifdef V8_USE_EXTERNAL_STARTUP_DATA
 bool InitializeV8ForPDFium(const std::string& exe_path,
diff --git a/testing/test_support.h b/testing/test_support.h
index a224114..d48d559 100644
--- a/testing/test_support.h
+++ b/testing/test_support.h
@@ -19,7 +19,11 @@
 
 // Converts a FPDF_WIDESTRING to a std::wstring.
 // Deals with differences between UTF16LE and wchar_t.
-std::wstring GetWideString(FPDF_WIDESTRING wstr);
+std::wstring GetPlatformWString(const FPDF_WIDESTRING wstr);
+
+// Returns a newly mallocated FPDF_WIDESTRING (caller must free()).
+// Deals with differences between UTF16LE and wchar_t.
+FPDF_WIDESTRING GetFPDFWideString(const std::wstring& wstr);
 
 #ifdef PDF_ENABLE_V8
 #ifdef V8_USE_EXTERNAL_STARTUP_DATA