Add an analysis option to disable cache flushing.

pkg/analyzer_cli/lib/src/driver.dart

Index: pkg/analyzer_cli/lib/src/driver.dart
diff --git a/pkg/analyzer_cli/lib/src/driver.dart b/pkg/analyzer_cli/lib/src/driver.dart
index ec779a7eb8dda662d1fdfe4fb65c148d403fe406..d46d3f531c61a47699b49c67bed7c2d7a639d084 100644
--- a/pkg/analyzer_cli/lib/src/driver.dart
+++ b/pkg/analyzer_cli/lib/src/driver.dart
@@ -311,6 +311,9 @@ class Driver implements CommandLineStarter {
         options.buildSummaryInputs, _previousOptions.buildSummaryInputs)) {
       return false;
     }
+    if (options.disableCacheFlushing != _previousOptions.disableCacheFlushing) {
+      return false;
+    }
     return true;
   }
 
@@ -663,6 +666,7 @@ class Driver implements CommandLineStarter {
       CommandLineOptions options) {
     AnalysisOptionsImpl contextOptions = new AnalysisOptionsImpl();
     contextOptions.trackCacheDependencies = false;
+    contextOptions.disableCacheFlushing = options.disableCacheFlushing;
     contextOptions.hint = !options.disableHints;
     contextOptions.enableInitializingFormalAccess =
         options.enableInitializingFormalAccess;