Support loading complete linearized PDF.
Support loading complete linearized PDF.

Previously, if a linearized PDF was loaded in a single callback (i.e. if
IsDocumentComplete was true in the call to LoadDocument), only the first
page of the document was visible because FPDFAvail_IsPageAvail was never
called for all other pages. This has been corrected.

BUG=572655

Review URL: https://codereview.chromium.org/1552603002

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#367046}

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