This version was built with branch chromium/6476 of PDFium

Changes

Commits between chromium/6462 and chromium/6476:

• Resolve unsafe buffer usage in cpdf_aaction.cpp and cpdf_action.cpp
• Fix unsafe buffer usage in xfa_basic_data.cpp
• Rework experimental FPDF_StructElement_Attr_* APIs
• Change FPDF_StructElement_Attr_* APIs to never return a reference
• Remove pragma unsafe_buffer_usage from CPDF_CMapParser.
• Remove #pragma allow_unsafe_buffers from cpdfsdk_appstream.cpp
• Narrow scope of UNSAFE_BUFFERS() in fpdfsdk/fpdf*.cpp
• Resolve unsafe buffer usage in CPDF_PSEngine
• Remove <string.h> inclusion from {Byte,Wide}String headers.
• Remove spurious includes of <string.h>.
• Remove file-wide unsafe_buffers pragmas from fpdfsdk/fpdf*.cpp
• Remove memcpy() from fpdfsdk/fpdf*.cpp (non-test files).
• Move pdfium_test.cc from samples/ to testing/
• Fix return of span_with_terminator() for empty string.
• Explain FPDFPage_RemoveObject() side effect on FPDF_TEXTPAGE handles
• Split off aes/sha headers from fx_crypt.h
• Roll third_party/googletest/src/ eff443c6e..fa6de7f43 (18 commits)
• Mass convert memmove() to FXSYS_memmove().
• Remove code that assumes CPDF_PageObjectHolder contains nullptrs
• Mass convert memset() to FXSYS_memset().
• Add fxcrt::Fill()
• Convert some memset(x, 0, sz) calls to aggregate initializations.
• Mass convert memcpy() to FXSYS_memcpy().
• Convert to std::array<> in CPDF_SimpleFont.
• Use #pragma allow_unsafe_buffers, not pdfium_unsafe_buffers_paths.txt
• Convert to std::array in cmaps/.
• Convert to extern std::array<> in /chromefontdata.
• Roll buildtools/clang_format/script/ e5337933f..3c0acd2d4 (23 commits)
• Roll Zlib from d076d8bd0898 to 7d77fb7fd66d (3 revisions)