Add plotters for the accelerator and finisher

These are what we used to tune them.

Change-Id: Ib492b717e38043a73c2d98e93c885d82df1513b6
diff --git a/aos/network/www/plotter.ts b/aos/network/www/plotter.ts
index 4c73a65..b4fc2eb 100644
--- a/aos/network/www/plotter.ts
+++ b/aos/network/www/plotter.ts
@@ -72,9 +72,10 @@
     return this._color;
   }
 
-  setColor(newColor: number[]) {
+  setColor(newColor: number[]): Line {
     this._color = newColor;
     this._hasUpdate = true;
+    return this;
   }
 
   // Get/set the size of the markers to draw, in pixels (zero means no markers).
@@ -82,9 +83,10 @@
     return this._pointSize;
   }
 
-  setPointSize(size: number) {
+  setPointSize(size: number): Line {
     this._pointSize = size;
     this._hasUpdate = true;
+    return this;
   }
 
   // Get/set whether we draw a line between the points (i.e., setting this to