Use a pdfium-specific unittest main rather than gtest's

We must initialize our partition allocator before calling into
any test cases.

We can then remove the FPDF_Test class, which did the same thing.

Change-Id: I614480fa474b2032052857a02e94781f15a27a4e
Reviewed-on: https://pdfium-review.googlesource.com/4473
Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Tom Sepez <tsepez@chromium.org>

xfa/fxfa/parser/xfa_utils_unittest.cpp

diff --git a/xfa/fxfa/parser/xfa_utils_unittest.cpp b/xfa/fxfa/parser/xfa_utils_unittest.cpp
index 6a1de85..aa46813 100644
--- a/xfa/fxfa/parser/xfa_utils_unittest.cpp
+++ b/xfa/fxfa/parser/xfa_utils_unittest.cpp
@@ -11,9 +11,7 @@
 #include "testing/test_support.h"
 #include "third_party/base/ptr_util.h"
 
-class XfaUtilsImpTest : public pdfium::FPDF_Test {};
-
-TEST_F(XfaUtilsImpTest, XFA_MapRotation) {
+TEST(XfaUtilsImpTest, XFA_MapRotation) {
   struct TestCase {
     int input;
     int expected_output;
@@ -29,7 +27,7 @@
   }
 }
 
-class XFANodeIteratorTest : public pdfium::FPDF_Test {
+class XFANodeIteratorTest : public testing::Test {
  public:
   class Node {
    public: