Remove PCE throwing as it can cancel background tasks (KT-19901)

Method can be called from the background task and be paused because
the write action is in progress. Throwing the PCE might stop the whole
task, that is wrong.

Explicit read action seems to be unneeded.

#KT-19901 Fixed

idea/src/org/jetbrains/kotlin/idea/injection/KotlinLanguageInjector.kt

@@ -38,7 +38,6 @@ import org.intellij.plugins.intelliLang.util.AnnotationUtilEx
 import org.jetbrains.kotlin.descriptors.FunctionDescriptor
 import org.jetbrains.kotlin.idea.caches.resolve.analyze
 import org.jetbrains.kotlin.idea.references.KtReference
-import org.jetbrains.kotlin.idea.runInReadActionWithWriteActionPriorityWithPCE
 import org.jetbrains.kotlin.idea.util.ProjectRootsUtil
 import org.jetbrains.kotlin.name.FqName
 import org.jetbrains.kotlin.psi.*
@@ -78,15 +77,17 @@ class KotlinLanguageInjector(
         val modificationCount = PsiManager.getInstance(project).modificationTracker.modificationCount
 
         val baseInjection = when {
-            needImmediateAnswer -> kotlinCachedInjection?.baseInjection ?: ABSENT_KOTLIN_INJECTION
+            needImmediateAnswer -> {
+                // Can't afford long counting or typing will be laggy. Force cache reuse even if it's outdated.
+                kotlinCachedInjection?.baseInjection ?: ABSENT_KOTLIN_INJECTION
+            }
             kotlinCachedInjection != null && (modificationCount == kotlinCachedInjection.modificationCount) ->
+                // Cache is up-to-date
                 kotlinCachedInjection.baseInjection
             else -> {
-                runInReadActionWithWriteActionPriorityWithPCE {
-                    val computedInjection = computeBaseInjection(ktHost, support, registrar) ?: ABSENT_KOTLIN_INJECTION
-                    ktHost.cachedInjectionWithModification = KotlinCachedInjection(modificationCount, computedInjection)
-                    computedInjection
-                }
+                val computedInjection = computeBaseInjection(ktHost, support, registrar) ?: ABSENT_KOTLIN_INJECTION
+                ktHost.cachedInjectionWithModification = KotlinCachedInjection(modificationCount, computedInjection)
+                computedInjection
             }
         }