Improve documentation for the tools for generating size checks, based on comm...

ppapi/tests/clang/README

-This is a directory for Clang plugins that are designed to do analysis and/or manipulation of PPAPI code.  Clang is an open-source C front-end that allows you to parse C, C++, or Objective-C code in to an abstract syntax tree (or AST) for processing.
+This is a directory for Clang plugins that are designed to do analysis and/or
+manipulation of PPAPI code.  Clang is an open-source C front-end that allows
+you to parse C, C++, or Objective-C code in to an abstract syntax tree (or AST)
+for processing.  This README assumes that you are working in a check-out of
+chromium.
 
-To use these plugins, you will need to get Clang.  Clang is rapidly changing, so you may want to download and build it yourself.  See the instructions here:
+To use these plugins, you will need to get Clang.  Clang is rapidly changing,
+so you may want to download and build it yourself.  See the instructions here:
 - http://clang.llvm.org/get_started.html
 
-To build the plugins, use the Makefile in this directory.  If you want the provided Makefile to work out-of-the-box, in step 2 of the instructions at the above URL, you should do the following:
+To build the plugins, use the Makefile in this directory.  If you want the
+provided Makefile to work out-of-the-box, in step 2 of the instructions at the
+above URL, you should do the following:
 > mkdir ~/llvm
 > cd ~/llvm
-Now continue with the svn co command to check out llvm in ~/llvm/llvm.
+Now continue with the svn co command to check out llvm in ~/llvm/llvm.  If you
+choose to build llvm in another location, you can use environment variables to
+force the Makefile to find your build of clang.  See the Makefile for details.
 
-To run a plugin, use clang with the -cc1 -load and -plugin flags and an otherwise normal build line.  For example, to run liBPrintNamesAndSizes.so, if you currently build like this:
+To run a plugin, use clang with the -cc1 -load and -plugin flags and an
+otherwise normal build line.  For example, to run liBPrintNamesAndSizes.so, if
+you currently build like this:
 g++ (build_options)
 Run this from the command-line instead:
-clang -cc1 -load ppapi/tests/clang/libPrintNamesAndSizes.so -plugin PrintNamesAndSizes (build_options)
+clang -cc1 -load ppapi/tests/clang/libPrintNamesAndSizes.so \
+  -plugin PrintNamesAndSizes (build_options)
 
 Plugins:
-PrintNamesAndSizes : print_names_and_sizes.cc
-Print information about all top-level type definitions.  You probably won't need to run it by itself;  instead see generate_ppapi_size_checks.py, which uses the plugin.
+  PrintNamesAndSizes : print_names_and_sizes.cc
+  Print information about all top-level type definitions.  You probably won't
+  need to run it by itself;  instead see generate_ppapi_size_checks.py, which
+  uses the plugin.  See print_names_and_sizes.cc for more detail on the plugin.
 
-Example command-line:
-  python generate_ppapi_size_checks.py --ppapi-root=/usr/local/google/chrome_build/src/ppapi
-  python generate_ppapi_size_checks.py --help
+  Example command-line:
+    python generate_ppapi_size_checks.py \
+        --ppapi-root=/usr/local/google/chrome_build/src/ppapi
+    python generate_ppapi_size_checks.py --help
 
 
-FindAffectedInterfaces : find_affected_interfaces.cc
-Given typenames as parameters, print out all types that are affected (including function pointer types and structs containing affected function pointer types) if the given type(s) change.  This is meant to be used for determining what interfaces are affected by a change to a struct.
+  FindAffectedInterfaces : find_affected_interfaces.cc
+  Given typenames as parameters, print out all types that are affected
+  (including function pointer types and structs containing affected function
+  pointer types) if the given type(s) change.  This is meant to be used for
+  determining what interfaces are affected by a change to a struct.
 
-Example command-line:
-  clang -cc1 -load ppapi/tests/clang/libFindAffectedInterfaces.so -plugin FindAffectedInterfaces -I. ppapi/tests/all_includes.h -plugin-arg-FindAffectedInterfaces "struct PP_VideoCompressedDataBuffer_Dev"
-  clang -cc1 -load tests/clang/libFindAffectedInterfaces.so -plugin FindAffectedInterfaces -I../ tests/all_c_includes.h -plugin-arg-FindAffectedInterfaces "struct PP_VideoCompressedDataBuffer_Dev,struct PP_Var"
+  Example command-line:
+    clang -cc1 -load ppapi/tests/clang/libFindAffectedInterfaces.so \
+        -plugin FindAffectedInterfaces -I. ppapi/tests/all_includes.h \
+        -plugin-arg-FindAffectedInterfaces \
+        "struct PP_VideoCompressedDataBuffer_Dev"
+    clang -cc1 -load tests/clang/libFindAffectedInterfaces.so \
+        -plugin FindAffectedInterfaces -I../ tests/all_c_includes.h \
+        -plugin-arg-FindAffectedInterfaces \
+        "struct PP_VideoCompressedDataBuffer_Dev,struct PP_Var"
 
-(This assumes that clang is in your path and you are running the plugin from the ppapi subdirectory in a chrome checkout).
+(This assumes that clang is in your path and you are running the plugin from
+ the ppapi subdirectory in a chrome checkout).