Update documentation for PDFium initialization.

Better explain PDFium initialization, and mention older initialization
APIs/configs will be deprecated in the future. Do similar comment
updates in public/fpdfview.h.

Bug: pdfium:1446
Change-Id: I76acd76827fad6fe6a1bdf76f13b7dc20329e513
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/64453
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>

docs/getting-started.md

diff --git a/docs/getting-started.md b/docs/getting-started.md
index 0cf2ff3..6077d21 100644
--- a/docs/getting-started.md
+++ b/docs/getting-started.md
@@ -30,10 +30,10 @@
 
 ## Initializing PDFium
 
-The first step to using PDFium is to initialize the library. Having done so,
-you'll need to destroy the library when you're finished. When initializing the
-library you provide the `FPDF_LIBRARY_CONFIG` parameters to
-`FPDF_InitLibraryWithConfig`.
+The first step to using PDFium is to initialize the library. Having done so, one
+must destroy the library with `FPDF_DestroyLibrary()` when finished. When
+initializing the library, provide the `FPDF_LIBRARY_CONFIG` parameters to
+`FPDF_InitLibraryWithConfig()`.
 
 ```c
 #include <fpdfview.h>
@@ -52,16 +52,19 @@
 }
 ```
 
-Currently the `config.version` must be set to `2`. `m_pUserFontPaths` can be
-used to override the font paths searched by PDFium. If you wish to use your
-own font paths pass a `NULL` terminated list of `const char*` paths to use.
+Currently the `config.version` must be set to `2`. Older versions works for
+backwards compatibility, but will be deprecated eventually.
+
+`m_pUserFontPaths` can be used to override the font paths searched by PDFium. To
+use a custom font paths, pass a `NULL` terminated list of `const char*` paths to
+use.
 
 `m_pIsolate` and `m_v8EmbedderSlot` are both used to configure the V8
-javascript engine. In the first case, you can provide an isolate through
-`m_pIsolate` for PDFium to use to store per-isolate data. Passing `NULL` will
-case PDFium to allocate a new isolate. `m_v8EmbedderSlot` is the embedder data
-slot to use in the v8::Isolate to store PDFium data. The value must be between
-0 and v8::Internals::kNumIsolateDataSlots. Typically, 0 is a good choice.
+JavaScript engine. For the V8 isolate, either provide an isolate through
+`m_pIsolate` for PDFium to use to store per-isolate data, or pass `NULL` to tell
+PDFium to allocate a new isolate. `m_v8EmbedderSlot` is the embedder data slot
+to use in the v8::Isolate to store PDFium data. The value must be in the range
+[0, `v8::Internals::kNumIsolateDataSlots`). Typically, 0 is a good choice.
 
 For more information on using Javascript see the [V8 Getting Started][pdfium-v8]
 guide.

public/fpdfview.h

diff --git a/public/fpdfview.h b/public/fpdfview.h
index 901d7db..0542b05 100644
--- a/public/fpdfview.h
+++ b/public/fpdfview.h
@@ -214,12 +214,14 @@
 //          None.
 // Comments:
 //          Convenience function to call FPDF_InitLibraryWithConfig() for
-//          backwards comatibility purposes.
+//          backwards compatibility purposes. This will be deprecated in the
+//          future.
 FPDF_EXPORT void FPDF_CALLCONV FPDF_InitLibrary();
 
 // Process-wide options for initializing the library.
 typedef struct FPDF_LIBRARY_CONFIG_ {
   // Version number of the interface. Currently must be 2.
+  // Support for version 1 will be deprecated in the future.
   int version;
 
   // Array of paths to scan in place of the defaults when using built-in
@@ -234,9 +236,9 @@
   void* m_pIsolate;
 
   // The embedder data slot to use in the v8::Isolate to store PDFium's
-  // per-isolate data. The value needs to be between 0 and
-  // v8::Internals::kNumIsolateDataLots (exclusive). Note that 0 is fine
-  // for most embedders.
+  // per-isolate data. The value needs to be in the range
+  // [0, |v8::Internals::kNumIsolateDataLots|). Note that 0 is fine for most
+  // embedders.
   unsigned int m_v8EmbedderSlot;
 } FPDF_LIBRARY_CONFIG;