AnalyticsPingManager makes eclipse unresponsive

We have our projects configured with gradle. Just to clarify, we also added the gwtNature to our Gwt projects, at least we tried. However, when doing so, Eclipse becomes unresponsive. This means that using intellisense freezes the workspace by 30 seconds or more. We observed a lot of log spam in the Eclipse log files:

```
ENTRY com.gwtplugins.gwt.eclipse.core 4 0 2016-12-07 16:42:11.937
!MESSAGE Cannot get version of GWT SDK "C:\workspaces\devtools\gradleHome\caches\modules-2\files-2.1\com.google.gwt\gwt-servlet\2.8.0\8fba7d39f9a341892cda502aacb2f5287bd49309", ensure it is configured properly
!STACK 0
java.lang.ClassNotFoundException: com.google.gwt.dev.About
at java.net.URLClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at com.google.gwt.eclipse.core.runtime.GwtSdk.getVersion(GwtSdk.java:467)
at com.google.gdt.eclipse.core.sdk.SdkUtils$MaxSdkVersionComputer.computeMaxSdkVersion(SdkUtils.java:46)
at com.google.gdt.eclipse.suite.update.usage.AnalyticsPingManager.getSdkVersions(AnalyticsPingManager.java:112)
at com.google.gdt.eclipse.suite.update.usage.AnalyticsPingManager.sendPing(AnalyticsPingManager.java:103)
at com.google.gdt.eclipse.suite.update.usage.AnalyticsPingManager.sendCompilationPing(AnalyticsPingManager.java:75)
at com.google.gdt.eclipse.suite.update.builders.UpdateTriggerCompilationParticipant.isActive(UpdateTriggerCompilationParticipant.java:37)
at org.eclipse.jdt.internal.core.JavaModelManager$CompilationParticipants.getCompilationParticipants(JavaModelManager.java:440)
at org.eclipse.jdt.internal.core.builder.JavaBuilder.initializeBuilder(JavaBuilder.java:589)
at org.eclipse.jdt.internal.core.builder.JavaBuilder.build(JavaBuilder.java:169)
at org.eclipse.core.internal.events.BuildManager$2.run(BuildManager.java:735)
at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
at org.eclipse.core.internal.events.BuildManager.basicBuild(BuildManager.java:206)
at org.eclipse.core.internal.events.BuildManager.basicBuild(BuildManager.java:246)
at org.eclipse.core.internal.events.BuildManager$1.run(BuildManager.java:301)
at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
at org.eclipse.core.internal.events.BuildManager.basicBuild(BuildManager.java:304)
at org.eclipse.core.internal.events.BuildManager.basicBuildLoop(BuildManager.java:360)
at org.eclipse.core.internal.events.BuildManager.build(BuildManager.java:383)
at org.eclipse.core.internal.events.AutoBuildJob.doBuild(AutoBuildJob.java:142)
at org.eclipse.core.internal.events.AutoBuildJob.run(AutoBuildJob.java:232)
at org.eclipse.core.internal.jobs.Worker.run(Worker.java:55)
```

First, could you add some more log information on which projects that happend?
Second, do we really need to recalculate everything, everytime? Can't there be some caching, or

We didn't have those problem with the old plugin. The workaround for now was simply not to add the gwt nature to the projects (or unticking 'Use Gwt'), resulting in not really using the GWT plugin.

Could it be that projects which are not using GWT, but have gwt-servlet on the classpath might cause some problems?

AnalyticsPingManager.java、特に sendPing と getSdkVersions から始め、stack trace を使って UpdateTriggerCompilationParticipant.java と GwtSdk.java を通る呼び出しを追跡します。プロジェクトコンテキストと SDK バージョンの繰り返し計算が、報告されたログスパムとフリーズにどのように影響しているかを特定します。完了条件には、より有用なプロジェクト固有のロギングと、不要な再計算の削減または回避が検証済みで含まれていることが必要です。

索引モデルが issue の本文から書いたものです。