Update instructions

Change-Id: Ic06ca33f07932a0bcc7100537208441ede795b78
diff --git a/README.md b/README.md
index 8d217a3..d94ae79 100644
--- a/README.md
+++ b/README.md
@@ -1,55 +1,86 @@
 # Binary Size Plugin for Gerrit
 
+## How it works
+
+The plugin queries tryjobs for the current patchset on Gerrit, and gets the
+`binary_sizes` property from each of them. It also queries the equivalent CI
+jobs for the same base revision, and gets the same property from them. It then
+displays the results in a table, with rows being the files (keys in
+`binary_sizes` dict), and the columns being:
+
+Size before | Size after | Size difference (including %) | File | Builder
+
 ## Usage
 
-This plugin is configured via the `buildbucket.config` file present in the
+This plugin is configured via the `binary-size.config` file present in the
 repo's `refs/meta/config` ref, as well as the same file in all repositories
 in the repo's inheritance chain (up to and including All-Projects).
 
-An example buildbucket.config is below:
+See an example of binary-size.config:
+
+https://webrtc.googlesource.com/src/+/refs/meta/config/binary-size.config
+
+Also a short snippet below:
 
 ```
 [host]
-  git = "chromium.googlesource.com"
-  gerrit = "chromium-review.googlesource.com"
+    git = "webrtc.googlesource.com"
+    gerrit = "webrtc-review.googlesource.com"
 
-[bucket "chromium.buildbucket.swarming"]
-  builder = infra_presubmit
-  builder = infra_linux64
-  builder = infra_mac
-  builder = infra_win
-[bucket "tryserver.infra"]
-  builder = Infra Presubmit
-  builder = Infra Linux Trusty 64 Tester
-  builder = Infra Linux Precise 32 Tester
-  builder = Infra Mac Tester
-  builder = Infra Win Tester
+[builder "luci.webrtc.try/linux_rel"]
+    base = "luci.webrtc.ci/Linux64 Release"
+
+[builder "luci.webrtc.try/win_x64_clang_rel"]
+    base = "luci.webrtc.ci/Win64 Release (Clang)"
 ```
 
-In the vast majority of cases, the `host.git` and `host.gerrit` values are
-global to the entire host, so that stanza is specified in the All-Projects
-repo. Buckets and builders, on the other hand, are almost always very
-repository-specific, and so are only specified in "leaf" repositories which
-are not in any other repo's inheritance chain.
+This contains a mapping between tryjob builders and equivalent postsubmit
+builders. Equivalent in the sense that if they ran with the same code, they
+would produce the same `binary_sizes`. The plugin queries builds only from
+buckets that are mentioned at least once. It is OK to specify builders that
+don't provide a `binary_sizes` property, they will just be ignored.
 
-All changes to `buildbucket.config` files are instantly reflected. There is no
+Note that populating the `binary_sizes` property is a separate responsibility,
+and it is up to you to implement in your recipes. It needs to be a dict like
+`{"some_file.so": 123456, ...}`. The values of the dict are treated as sizes in
+bytes.
+
+All changes to `binary-size.config` files are instantly reflected. There is no
 caching period or need to restart the server.
 
+### Dependencies
+
+This plugin **requires** the [buildbucket][] plugin in order to search builds.
+Ensure that they are both installed, or prepare to see errors in the browser's
+console.
+
 ## Development
 
-### To use with the polygerrit-ui server against live data
+```bash
+git clone --recursive https://gerrit.googlesource.com/gerrit
+cd gerrit/plugins
 
-Use the script run-with-prod-data.sh; this creates a temporary directory
-with the plugin source in the expected layout and then invokes
-`polygerrit-ui/run-server.sh`. Example invocation:
+git clone https://chromium.googlesource.com/infra/gerrit-plugins/buildbucket
+cd buildbucket
+ln -s src/main/resources/static static  # May be unneeded in the future.
+cd ..
 
+git clone https://chromium.googlesource.com/infra/gerrit-plugins/binary-size
+cd binary-size
 ```
-GERRIT_DIR=~/gerrit ./run-with-prod-data.sh
+
+### Run the polygerrit-ui server against live data
+
+Use the script `run-with-prod-data.sh` (based on `polygerrit-ui/run-server.sh`).
+You may change some paths by setting environment variables, for example:
+
+```bash
+GERRIT_DIR="$HOME/gerrit" ./run-with-prod-data.sh
 ```
 
 ### Testing
 
-```
+```bash
 # Install dependencies.
 npm install -g bower
 npm install -g web-component-tester
@@ -63,3 +94,5 @@
 
 Note: Testing is disabled for Safari due to
 [this issue](https://github.com/Polymer/web-component-tester/issues/411).
+
+[buildbucket]: https://chromium.googlesource.com/infra/gerrit-plugins/buildbucket/