Tighten max heap size for SystemUI benchmark to 1680m

This also adds support for dumping the heap at the end of tree shaking.

Change-Id: Icd93a162444b3caa8cd282e1726fea3e9569c050

src/main/java/com/android/tools/r8/shaking/Enqueuer.java

diff --git a/src/main/java/com/android/tools/r8/shaking/Enqueuer.java b/src/main/java/com/android/tools/r8/shaking/Enqueuer.java
index 0752c87..0d44c76 100644
--- a/src/main/java/com/android/tools/r8/shaking/Enqueuer.java
+++ b/src/main/java/com/android/tools/r8/shaking/Enqueuer.java
@@ -3986,6 +3986,7 @@
     } else {
       assert proguardCompatibilityActionsBuilder == null;
     }
+    options.dumpHeap(mode.toString().toLowerCase());
     timing.end();
     if (mode.isWhyAreYouKeeping()) {
       // For why are you keeping the information is reported through the kept graph callbacks and

tools/run_benchmark.py

diff --git a/tools/run_benchmark.py b/tools/run_benchmark.py
index e8c72b8..a6248aa 100755
--- a/tools/run_benchmark.py
+++ b/tools/run_benchmark.py
@@ -230,8 +230,8 @@
         xms = '32g'
         xmx = '32g'
     elif options.benchmark == 'SystemUIAppGc':
-        xms = '1760m'
-        xmx = '1760m'
+        xms = '1680m'
+        xmx = '1680m'
     if options.heap_size:
         xms = options.heap_size
         xmx = options.heap_size