Fix a memory leak in FPDFPageFuncEmbeddertest.

R=dsinclair@chromium.org

Review URL: https://codereview.chromium.org/1514283002 .
diff --git a/core/src/fpdfapi/fpdf_render/fpdf_render_pattern_embeddertest.cpp b/core/src/fpdfapi/fpdf_render/fpdf_render_pattern_embeddertest.cpp
index 744c4e5..176c923 100644
--- a/core/src/fpdfapi/fpdf_render/fpdf_render_pattern_embeddertest.cpp
+++ b/core/src/fpdfapi/fpdf_render/fpdf_render_pattern_embeddertest.cpp
@@ -11,6 +11,7 @@
   // Test shading where object is a dictionary instead of a stream.
   EXPECT_TRUE(OpenDocument("bug_547706.pdf"));
   FPDF_PAGE page = LoadPage(0);
-  RenderPage(page);
+  FPDF_BITMAP bitmap = RenderPage(page);
+  FPDFBitmap_Destroy(bitmap);
   UnloadPage(page);
 }