Display content of the annotation when mouse hover.

Each annotation has its contents, and users should be able to see the
contents. In this patch, PDFium creates a Popup annotation for each
annotation and stores the author and the content. When a user mouse
hover on the annotation, PDFium draws the corresponding Popup annotation
and displays the content.

Also, roll DEPS for testing/corpus to 5867fa6.

BUG=62625

Review-Url: https://codereview.chromium.org/2273893002
diff --git a/DEPS b/DEPS
index d168db7..7729241 100644
--- a/DEPS
+++ b/DEPS
@@ -14,7 +14,7 @@
   'gmock_revision': '29763965ab52f24565299976b936d1265cb6a271',
   'gtest_revision': '8245545b6dc9c4703e6496d1efd19e975ad2b038',
   'icu_revision': '2341038bf72869a5683a893a2b319a48ffec7f62',
-  'pdfium_tests_revision': 'afbac944ba4b41252e4bd16372f27806bc0ed924',
+  'pdfium_tests_revision': '5867fa68fa3e00016d3e31374e84eb01a3db6ac7',
   'skia_revision': '3bf7509c3f68aefbe5f8b2ea5888319a71a91d2d',
   'tools_memory_revision': '427f10475e1a8d72424c29d00bf689122b738e5d',
   'trace_event_revision': '54b8455be9505c2cb0cf5c26bb86739c236471aa',