Fix various issues with Markdown docs

docs/common_build_tasks.md

 # Common Build Tasks
 
 The Chromium build system is a complicated beast of a system, and it is not very
 well documented beyond the basics of getting the source and building the
 Chromium product. This page has more advanced information about the build
 system.
 
 If you're new to Chromium development, read the
 [getting started guides](http://dev.chromium.org/developers/how-tos/get-the-code).
 
@@ skipping 49 matching lines @@
 
 ## Configuring the Build
 
 ### Environment Variables
 
 There are various environment variables that can be passed to the metabuild
 system GYP when generating project files. This is a summary of them:
 
 TODO(andybons): Convert to list.
 
-| GYP\_DEFINES | A set of key=value pairs separated by space that will set default values of variables used in .gyp and .gypi files |
-|:-------------|:-------------------------------------------------------------------------------------------------------------------|
-| GYP\_GENERATORS | The specific generator that creates build-system specific files                                                    |
-| GYP\_GENERATOR\_FLAGS | Flags that are passed down to the tool that generates the build-system specific files                              |
-| GYP\_GENERATOR\_OUTPUT | The directory that the top-level build output directory is relative to                                             |
+|:-------------|:--------------------------------------------------------------|
+| `GYP_DEFINES` | A set of key=value pairs separated by space that will set default values of variables used in .gyp and .gypi files |
+| `GYP_GENERATORS` | The specific generator that creates build-system specific files |
+| `GYP_GENERATOR_FLAGS` | Flags that are passed down to the tool that generates the build-system specific files |
+| `GYP_GENERATOR_OUTPUT` | The directory that the top-level build output directory is relative to |
 
 Note also that GYP uses CPPFLAGS, CFLAGS, and CXXFLAGS when generating ninja
 files (the values at build time = ninja run time are _not_ used); see
 [gyp/generator/ninja.py](https://code.google.com/p/chromium/codesearch#chromium/src/tools/gyp/pylib/gyp/generator/ninja.py&q=cxxflags).
 
 ### Variable Files
 
 If you want to keep a set of variables established, there are a couple of magic
 files that GYP reads:
 
 #### chromium.gyp\_env
 
 Next to your top-level `/src/` directory, create a file called
 `chromium.gyp_env`. This holds a JSON dictionary, with the keys being any of the
 above environment variables. For the full list of supported keys, see
 [/src/build/gyp_helper.py](/build/gyp_helper.py).
 
-``` {
+```
+{
   'variables': {
     'mac_strip_release': 0,
   }, 'GYP_DEFINES':
     'clang=1 ' 'component=shared_library ' 'dcheck_always_on=1 '
-} ```
+}
+```
 
 #### include.gyp
 
 Or globally in your home directory, create a file `~/.gyp/include.gypi`.
 
 #### supplement.gypi
 
 The build system will also include any files named `/src/*/supplement.gypi`,
 which should be in the same format as include.gyp above.
 
@@ skipping 39 matching lines @@
 
     $ GYP_DEFINES="branding=Chrome buildtype=Official" gclient runhooks
 
 Then building the `chrome` target will produce the official build. This tip can
 be used in conjunction with changing the output directory, since changing these
 defines will rebuild the world.
 
 Also note that some GYP\_DEFINES flags are incompatible with the official build.
 If you get an error when you try to build, try removing all your flags and start
 with just the above ones.