Roll pdfium. This brings in:

df449c0  Change '>=' back to '>' in extension.h due to bad fix
2ee9c3a  gclient DEPS file for auto checking out deps
9047b8b  Clean up meaningless branch on commented-out code.
ef72d48  Fix the problem that memory is accessed after released due to invalid type-cast
1b9c5c4  Fix use-after-free in CPDF_Color::~CPDF_Color
06a8c87  Fix unninitialized 'tmp' in CJBig2_Image::composeTo_opt2
7b99cd3  Remove unused |m_pEvi| field.
f47ab54  Fix a segmentation fault in CPDF_DataAvail::CheckPage due to invalid usage of i++

BUG=392719,387979,387811,387774,375773,400662
TBR=tsepez@chromium.org
NOTRY=true

Review URL: https://codereview.chromium.org/449093003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@288186 0039d316-1c4b-4281-b951-d872f2087c98

DEPS

@@ -77,7 +77,7 @@ vars = {
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling PDFIum
   # and whatever else without interference from each other.
-  "pdfium_revision": "465c2a84ba709d932040c9e80db508e93c138da6",
+  "pdfium_revision": "df449c0eb4b1fb5583da71265faf50a9a520be3c",
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling openmax_dl
   # and whatever else without interference from each other.