Calculate numPlotsY from height

Add a compensating change to make A8 plot
size 512x512.

Change-Id: Iaca4327d07c629143ec7dfb9e294b8fed4b8135a
Reviewed-on: https://skia-review.googlesource.com/152420
Reviewed-by: Jim Van Verth <jvanverth@google.com>
Commit-Queue: Herb Derby <herb@google.com>
diff --git a/src/gpu/text/GrAtlasManager.cpp b/src/gpu/text/GrAtlasManager.cpp
index e589b20..ddd0b03 100644
--- a/src/gpu/text/GrAtlasManager.cpp
+++ b/src/gpu/text/GrAtlasManager.cpp
@@ -52,7 +52,7 @@
     fAtlasConfigs[kA8_GrMaskFormat].fWidth = maxDim;
     fAtlasConfigs[kA8_GrMaskFormat].fHeight = maxDim;
     fAtlasConfigs[kA8_GrMaskFormat].fPlotWidth = maxPlot;
-    fAtlasConfigs[kA8_GrMaskFormat].fPlotHeight = minPlot;
+    fAtlasConfigs[kA8_GrMaskFormat].fPlotHeight = maxPlot;
 
     // A565 and ARGB use maxDim x minDim.
     fAtlasConfigs[kA565_GrMaskFormat].fWidth = minDim;