Refresh README.md:

- Refer to Chromium's prerequisites page, rather than trying to maintain
  a separate one.
- Mention build/install-build-deps.sh is for Linux only.
- Clarify who "we" are in the doc.
- Fix a broken intra-document link.

Change-Id: I1cca21e5179ff6e1aabe25443564cf69c2117826
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/80190
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>
diff --git a/README.md b/README.md
index 5c4472f..b6a0396 100644
--- a/README.md
+++ b/README.md
@@ -2,27 +2,13 @@
 
 ## Prerequisites
 
-Get the Chromium depot\_tools via the
-[instructions](https://www.chromium.org/developers/how-tos/install-depot-tools).
-This provides the gclient utility needed below and many other tools needed for
-PDFium development.
+PDFium uses the same build tooling as Chromium. See the platform-specific
+Chromium build instructions to get started, but replace Chromium's
+"Get the code" instructions with [PDFium's](#get-the-code).
 
-Also install Python, Subversion, and Git and make sure they're in your path.
-
-
-### Windows development
-
-PDFium uses the same build tool as Chromium:
-
-#### Open source contributors
-Please refer to
-[Chromium's Visual Studio set up](https://chromium.googlesource.com/chromium/src/+/main/docs/windows_build_instructions.md#visual-studio)
-for requirements and instructions on build environment configuration.
-
-Run `set DEPOT_TOOLS_WIN_TOOLCHAIN=0`, or set that variable in your global
-environment.
-
-Compilation is done through Ninja, **not** Visual Studio.
+*   [Chromium Linux build instructions](https://chromium.googlesource.com/chromium/src/+/main/docs/linux/build_instructions.md)
+*   [Chromium Mac build instructions](https://chromium.googlesource.com/chromium/src/+/main/docs/mac_build_instructions.md)
+*   [Chromium Windows build instructions](https://chromium.googlesource.com/chromium/src/+/main/docs/windows_build_instructions.md)
 
 ### CPU Architectures supported
 
@@ -42,7 +28,7 @@
 @google.com credentials**. Enter "0" if asked for a project-id.
 
 Once you've done this, the toolchain will be installed automatically for
-you in the [Generate the build files](#GenBuild) step below.
+you in the [Generate the build files](#generate-the-build-files) step below.
 
 The toolchain will be in `depot_tools\win_toolchain\vs_files\<hash>`, and
 windbg can be found in
@@ -53,9 +39,10 @@
 
 ## Get the code
 
-The name of the top-level directory does not matter. In our examples, we use
-"repo". This directory must not have been used before by `gclient config` as
-each directory can only house a single gclient configuration.
+The name of the top-level directory does not matter. In the following example,
+the directory name is "repo". This directory must not have been used before by
+`gclient config` as each directory can only house a single gclient
+configuration.
 
 ```
 mkdir repo
@@ -65,8 +52,8 @@
 cd pdfium
 ```
 
-Additional build dependencies need to be installed by running the following from
-the `pdfium` directory.
+On Linux, additional build dependencies need to be installed by running the
+following from the `pdfium` directory.
 
 ```
 ./build/install-build-deps.sh
@@ -74,7 +61,7 @@
 
 ## Generate the build files
 
-We use GN to generate the build files and [Ninja](https://ninja-build.org/)
+PDFium uses GN to generate the build files and [Ninja](https://ninja-build.org/)
 to execute the build files.  Both of these are included with the
 depot\_tools checkout.
 
@@ -198,7 +185,8 @@
 ## Embedding PDFium in your own projects
 
 The public/ directory contains header files for the APIs available for use by
-embedders of PDFium. We endeavor to keep these as stable as possible.
+embedders of PDFium. The PDFium project endeavors to keep these as stable as
+possible.
 
 Outside of the public/ directory, code may change at any time, and embedders
 should not directly call these routines.
@@ -230,9 +218,8 @@
 
 ## Bugs
 
- We use this
-[bug tracker](https://bugs.chromium.org/p/pdfium/issues/list), but for security
-bugs, please use
+PDFium uses this [bug tracker](https://bugs.chromium.org/p/pdfium/issues/list),
+but for security bugs, please use
 [Chromium's security bug template](https://bugs.chromium.org/p/chromium/issues/entry?template=Security%20Bug)
 and add the "Cr-Internals-Plugins-PDF" label.