Markdown instruction how to generate code coverage for LayoutNG

third_party/WebKit/Source/core/layout/ng/README.md

 # LayoutNG #
 
 This directory contains the implementation of Blink's new layout engine
 "LayoutNG".
 
 This README can be viewed in formatted form [here](https://chromium.googlesource.com/chromium/src/+/master/third_party/WebKit/Source/core/layout/ng/README.md).
 
 The original design document can be seen [here](https://docs.google.com/document/d/1uxbDh4uONFQOiGuiumlJBLGgO4KDWB8ZEkp7Rd47fw4/edit).
 
 ## High level overview ##
@@ skipping 40 matching lines @@
 
   - `CollectInlines`: Performs a depth-first scan of the container collecting
     all non-atomic inlines and `TextNodes`s. Atomic inlines are represented as a
     unicode object replacement character but are otherwise skipped.
     Each non-atomic inline and `TextNodes` is fed to a
     [NGLayoutInlineItemsBuilder](ng_layout_inline_items_builder.h) instance
     which collects the text content for all non-atomic inlines in the container.
 
     During this process white-space is collapsed and normalized according to CSS
     white-space processing rules.
-    
+
   - `SegmentText`: Performs BiDi segmentation using
     [NGBidiParagraph](ng_bidi_paragraph.h).
-    
+
     TODO(kojii): Fill out
-    
+
   - `ShapeText`: Shapes the resolved BiDi runs using HarfBuzz.
     TODO(eae): Fill out
 
 ### Fragment Tree ###
 
 TODO(layout-dev): Document with lots of pretty pictures.
 
 ### Constraint Spaces ###
 
 TODO(layout-dev): Document with lots of pretty pictures.
 
 ## Block Flow Algorithm ##
 
 This section contains details specific to the
 [NGBlockLayoutAlgorithm](ng_block_layout_algorithm.h).
 
 ### Collapsing Margins ###
 
 TODO(layout-dev): Document with lots of pretty pictures.
 
 ### Float Positioning ###
 
 TODO(layout-dev): Document with lots of pretty pictures.
+
+### Code coverage ###
+
+The latest code coverage (from Feb 14 2017) can be found [here](https://glebl.users.x20web.corp.google.com/www/layout_ng_code_coverage/index.html).
+Here is the instruction how to generate a new result.
+
+#### Environment setup ####
+ 1. Set up Chromium development environment for Windows
+ 2. Download DynamoRIO from [www.dynamorio.org](www.dynamorio.org)
+ 3. Extract downloaded DynamoRIO package into your chromium/src folder.
+ 4. Get dynamorio.git and extract it into your chromium/src folder `git clone https://github.com/DynamoRIO/dynamorio.git`
+ 5. Install Node js from https://nodejs.org/en/download/
+ 6. Install lcov-merger dependencies:  `npm install vinyl, npm install vinyl-fs`
+ 7. Install Perl from https://www.perl.org/get.html#win32
+ 8. Get lcov-result-merger and extract into your chromium/src folder `git clone https://github.com/mweibel/lcov-result-merger`
+
+#### Generating code coverage ####
+* Build the unit tets target with debug information
+`chromium\src> ninja -C out\Debug webkit_unit_tests`
+* Run DynamoRIO with drcov tool
+`chromium\src>DynamoRIO\bin64\drrun.exe -t drcov -- .\out\Debug\webkit_unit_tests.exe --gtest_filter=NG*`
+* Convert the output information to lcov format
+`chromium\src>for %file in (*.log) do DynamoRIO\tools\bin64\drcov2lcov.exe -input %file -output %file.info -src_filter layout/ng -src_skip_filter _test`
+* Merge all lcov files into one file
+`chromium\src>node lcov-result-merger\bin\lcov-result-merger.js *.info output.info`
+* Generate the coverage html from the master lcov file
+`chromium\src>C:\Perl64\bin\perl.exe dynamorio.git\third_party\lcov\genhtml output.info -o output`